View source for Seminar with Alan Kay on Object Oriented Programming

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<subtitle id='00:00:00'> [Music] good idea to put up a slide warning you</subtitle>
<subtitle id='00:00:07'>there might be some IBM jokes of course this isn't I guess this isn't really IBM</subtitle>
<subtitle id='00:00:12'>country out here although I did hear a rumor that you're still programmed in</subtitle>
<subtitle id='00:00:19'>Fortran quite a bit and even the dread word COBOL was heard so maybe it's</subtitle>
<subtitle id='00:00:25'>worthwhile you know object-oriented programming is actually a rather old technology it is</subtitle>
<subtitle id='00:00:34'>just a few years younger in fact than the kind of programming technology that</subtitle>
<subtitle id='00:00:40'>most people are used to that of data structures manipulated by procedures and</subtitle>
<subtitle id='00:00:46'>for various reasons it has not come into</subtitle>
<subtitle id='00:00:50'>currency into vogue until the last couple of years but it's actually about</subtitle>
<subtitle id='00:00:55'>25 years ago I wrote my first program that I would call object-oriented in</subtitle>
<subtitle id='00:01:00'>1962 and people have been writing</subtitle>
<subtitle id='00:01:04'>programs in that style even earlier than</subtitle>
<subtitle id='00:01:08'>that in my particular case I was a programmer in the Air Force at Air</subtitle>
<subtitle id='00:01:15'>Training Command in 1962 the there were</subtitle>
<subtitle id='00:01:19'>no standardized operating systems of course that's true today</subtitle>
<subtitle id='00:01:25'>but back then there was actually a reason for it</subtitle>
<subtitle id='00:01:29'>nobody had gotten around to the idea of thinking it it might be useful and Air</subtitle>
<subtitle id='00:01:33'>Training Command had a problem of moving</subtitle>
<subtitle id='00:01:38'>tapes tapes with records of various</subtitle>
<subtitle id='00:01:43'>kinds on them from one Air Training Command base to another the machines</subtitle>
<subtitle id='00:01:49'>back borrows two twenties which were</subtitle>
<subtitle id='00:01:53'>machines that have had about five thousand characters of of storage we're</subtitle>
<subtitle id='00:01:58'>about the size of this room and we're great coffee warmers my image of them of</subtitle>
<subtitle id='00:02:04'>the 220 is with a this huge set of boxes with a row of pots on top trapping the</subtitle>
<subtitle id='00:02:12'>heat is a came out now the problem that</subtitle>
<subtitle id='00:02:17'>they had was that there is no way to standardize on what the formats of the</subtitle>
<subtitle id='00:02:22'>different records were they changed and the operating system he was usually just</subtitle>
<subtitle id='00:02:28'>the kind of a loading program and so there was no way of standardizing on</subtitle>
<subtitle id='00:02:32'>that and they wondered how can we actually read these data records if</subtitle>
<subtitle id='00:02:38'>everything is constantly changing and nothing holds still somebody thought up</subtitle>
<subtitle id='00:02:42'>a great idea that idea was to have the</subtitle>
<subtitle id='00:02:48'>records shipped in the following format the each tape file had three sections to</subtitle>
<subtitle id='00:02:55'>it the front section was fairly short it had a bunch of relative pointers into</subtitle>
<subtitle id='00:03:01'>the second section which contained a bunch of Burroughs 220 code and that</subtitle>
<subtitle id='00:03:07'>code knew how to deal with a third section which had the actual data records and so what you got when you</subtitle>
<subtitle id='00:03:15'>read a record from this machine was you</subtitle>
<subtitle id='00:03:20'>read that record the first two parts of the of the record into storage use the</subtitle>
<subtitle id='00:03:29'>the front part of it which were these indirect jumps into the second part of</subtitle>
<subtitle id='00:03:34'>it the code as the protocol for dealing with the tape</subtitle>
<subtitle id='00:03:38'>they're usually about 20 or 30 what we would call messages today but 20 or 30</subtitle>
<subtitle id='00:03:44'>entries in the in that first table and the code that came along with the tape</subtitle>
<subtitle id='00:03:49'>records knew how to deal with all the data so in current day terms what the</subtitle>
<subtitle id='00:03:55'>Air Training Command was doing I think it was as far ago as the late 50s was to</subtitle>
<subtitle id='00:04:01'>ship an entire class of objects the</subtitle>
<subtitle id='00:04:05'>class was shipped with the protocol with</subtitle>
<subtitle id='00:04:10'>all of the code and with all of the data in a form in which you did not have to</subtitle>
<subtitle id='00:04:14'>penetrate any of it in order to make use of it that was used for a number of</subtitle>
<subtitle id='00:04:20'>years as a technique until COBOL came in</subtitle>
<subtitle id='00:04:24'>and the Air Force forced all of the all of those good ideas to go away in order</subtitle>
<subtitle id='00:04:29'>to standardize and COBOL which is a much weaker conception going back to the</subtitle>
<subtitle id='00:04:33'>notion of data structures that are fragile now I understand that we have a</subtitle>
<subtitle id='00:04:39'>kind of a mixed audience today in that some of the people in the room are</subtitle>
<subtitle id='00:04:43'>rather knowledgeable about object-oriented programming some of the</subtitle>
<subtitle id='00:04:47'>people in the audience are here out of curiosity so I made a kind of a mixed</subtitle>
<subtitle id='00:04:55'>talk what I would like to do is to give</subtitle>
<subtitle id='00:04:59'>you sort of a perspective on where object-oriented programming has been</subtitle>
<subtitle id='00:05:04'>what it's what it's been done without without getting to historical about it</subtitle>
<subtitle id='00:05:08'>but try and give you an understanding of why it has contributed so much in a</subtitle>
<subtitle id='00:05:14'>number of areas other than just writing programs that don't break one of those</subtitle>
<subtitle id='00:05:21'>is user interface which is a very important area and there are some direct</subtitle>
<subtitle id='00:05:26'>relations chips to the way we think about objects and the way we think about</subtitle>
<subtitle id='00:05:31'>user interface and then take you into</subtitle>
<subtitle id='00:05:36'>the future a little bit and show you some of the things in which object-oriented programming is being</subtitle>
<subtitle id='00:05:40'>used for in research directions and then try and open up the form into issues</subtitle>
<subtitle id='00:05:47'>because my belief is that the basic ideas of object-oriented</subtitle>
<subtitle id='00:05:51'>are quite simple maybe too simple to be</subtitle>
<subtitle id='00:05:56'>popular until we absolutely require</subtitle>
<subtitle id='00:06:00'>simplicity in this stage of 2 million line programs but that the most</subtitle>
<subtitle id='00:06:05'>interesting thing about object-oriented programming are the are the various</subtitle>
<subtitle id='00:06:09'>issues and the styles for using it and those haven't settled yet so my</subtitle>
<subtitle id='00:06:15'>reference to the IBM joke I think a good good way of starting out the talk is</subtitle>
<subtitle id='00:06:19'>that last year it was even reported in</subtitle>
<subtitle id='00:06:23'>Business Week as a significant event IBM had its first object-oriented colloquium</subtitle>
<subtitle id='00:06:31'>it was such an amazing thing they believe that only 25 people would attend</subtitle>
<subtitle id='00:06:37'>and in fact 500 attended and they had to turn away 500 people from within IBM I</subtitle>
<subtitle id='00:06:45'>got invited to give the keynote talk part of what I'm going to show you today is from that keynote talk and standing</subtitle>
<subtitle id='00:06:52'>there in Yorktown Heights giving the</subtitle>
<subtitle id='00:06:56'>giving the talk I was reminded of William James's characterization of the</subtitle>
<subtitle id='00:07:01'>three stages that an idea goes through the first stage is the new idea is</subtitle>
<subtitle id='00:07:07'>characterized as the work of mad been</subtitle>
<subtitle id='00:07:11'>absolutely denounced out of hand a few years later goes through a different</subtitle>
<subtitle id='00:07:17'>stage when it's remarked on as being commonplace and obvious all the time</subtitle>
<subtitle id='00:07:21'>then the third and final stage is when the original denouncer is claimed to</subtitle>
<subtitle id='00:07:25'>have invented it and we are now in that</subtitle>
<subtitle id='00:07:30'>third stage for object-oriented programming because now that iBM has decided to adopt I've yet</subtitle>
<subtitle id='00:07:36'>I'm Jacobian program we can be quite sure that it's actually obsolete</subtitle>
<subtitle id='00:07:40'>and on its way out</subtitle>
<subtitle id='00:07:45'>so now before before I get into the</subtitle>
<subtitle id='00:07:51'>historical part what I thought I'd do is</subtitle>
<subtitle id='00:07:55'>for those people who are not acquainted with it at all I thought I would just</subtitle>
<subtitle id='00:08:00'>say a couple of couple of words about</subtitle>
<subtitle id='00:08:04'>what it what I mean when I say object-oriented programming and I have a</subtitle>
<subtitle id='00:08:11'>I have a very simple diagram here for me</subtitle>
<subtitle id='00:08:16'>the whole notion of objects was</subtitle>
<subtitle id='00:08:20'>triggered off by seeing a number of different systems some of them in</subtitle>
<subtitle id='00:08:26'>computer science but the first ones that I looked at were actually biological I</subtitle>
<subtitle id='00:08:30'>have a degree in molecular biology and</subtitle>
<subtitle id='00:08:35'>one of the things that struck me when I was studying molecular biology many years ago was that compared to the kinds</subtitle>
<subtitle id='00:08:43'>of structures that we tend to build here on earth the average biological</subtitle>
<subtitle id='00:08:48'>structure is more than a thousand times as complex both as regard to the number</subtitle>
<subtitle id='00:08:54'>of different parts it has and to the</subtitle>
<subtitle id='00:08:59'>complexity that has to be controlled for</subtitle>
<subtitle id='00:09:03'>instance a grand piano is a rather complex machine has about 20,000 parts</subtitle>
<subtitle id='00:09:09'>which surprises most musicians you don't even think that they're actually playing</subtitle>
<subtitle id='00:09:13'>on a machine they think of it as an instrument and the instrument by</subtitle>
<subtitle id='00:09:18'>definition can't be a machine but in fact it is a machine has about 20,000</subtitle>
<subtitle id='00:09:22'>parts our bodies have approximately a</subtitle>
<subtitle id='00:09:27'>trillion cells in them and each cell is</subtitle>
<subtitle id='00:09:31'>rather complex each cell has many millions of components in its own right</subtitle>
<subtitle id='00:09:37'>so one of the ways nature discovered to</subtitle>
<subtitle id='00:09:43'>control complexity and the kinds of interactions that are likely to happen</subtitle>
<subtitle id='00:09:48'>is to try and incapsulate them in</subtitle>
<subtitle id='00:09:52'>various ways this is a familiar principle to us it's something that we use in regular program</subtitle>
<subtitle id='00:09:56'>as well trying to encapsulate and the</subtitle>
<subtitle id='00:10:00'>question you're always asking when you encapsulate we're going to ask this</subtitle>
<subtitle id='00:10:04'>quite a bit later is just what is encapsulated what kinds of things are we</subtitle>
<subtitle id='00:10:10'>trying to control are usually in regular programming what we encapsulate are</subtitle>
<subtitle id='00:10:15'>sections of programs that occasionally</subtitle>
<subtitle id='00:10:19'>will try and encapsulate with regard to a protocol for dealing with some system</subtitle>
<subtitle id='00:10:23'>we don't want to inquire about the internals of what biological systems</subtitle>
<subtitle id='00:10:28'>encapsulate is the actual environment in</subtitle>
<subtitle id='00:10:32'>which most important processing takes place there are very few object-oriented</subtitle>
<subtitle id='00:10:38'>programming languages that go that far the average object-oriented programming</subtitle>
<subtitle id='00:10:43'>language encapsulate snot the environment but in fact something like</subtitle>
<subtitle id='00:10:50'>the state of a data structure along with</subtitle>
<subtitle id='00:10:54'>the procedures that know how to intimately manipulate it and try and tie</subtitle>
<subtitle id='00:10:58'>those two areas together in a way that</subtitle>
<subtitle id='00:11:02'>they cannot be penetrated from the outside when people speak of an</subtitle>
<subtitle id='00:11:09'>object-oriented programming language like Objective C or C++ they're talking</subtitle>
<subtitle id='00:11:14'>about even less than that because they're the encapsulation is almost a</subtitle>
<subtitle id='00:11:21'>convention it's done by means of macros</subtitle>
<subtitle id='00:11:25'>the amount of protection at runtime that</subtitle>
<subtitle id='00:11:29'>is delivered is rather low so there all</subtitle>
<subtitle id='00:11:33'>of these gradations now biological systems encapsulate with a vengeance</subtitle>
<subtitle id='00:11:37'>because nature discovered that if you</subtitle>
<subtitle id='00:11:41'>give each cell its own little captured ocean and let it devote about 90% of its</subtitle>
<subtitle id='00:11:49'>actual energies to simply protecting</subtitle>
<subtitle id='00:11:53'>itself from the outside world as though the outside world were hostile then you</subtitle>
<subtitle id='00:11:58'>get a situation where you can build very large structures rather safely and</subtitle>
<subtitle id='00:12:03'>encapsulated is not just the saline solution not just the organic Moloch</subtitle>
<subtitle id='00:12:10'>skills but also encapsulated and not</subtitle>
<subtitle id='00:12:14'>just the programs that drive the cell but in fact encapsulated in biological</subtitle>
<subtitle id='00:12:19'>organisms as many of you are aware is the entire plan for the entire structure</subtitle>
<subtitle id='00:12:25'>okay now we don't generally do that when</subtitle>
<subtitle id='00:12:29'>we write an object-oriented program but in fact people are starting to do that</subtitle>
<subtitle id='00:12:33'>now in artificial intelligence and people who are interested can can bring</subtitle>
<subtitle id='00:12:38'>this up later so my particular</subtitle>
<subtitle id='00:12:52'>my particular motivation</subtitle>
<subtitle id='00:12:59'>when I started thinking about objects</subtitle>
<subtitle id='00:13:06'>was simply that of biological cells and</subtitle>
<subtitle id='00:13:11'>one of the things that is difficult to escape when you look at biological cells</subtitle>
<subtitle id='00:13:16'>is first the extent to which the outside</subtitle>
<subtitle id='00:13:20'>world is kept away from the cell membrane and then the other thing is is</subtitle>
<subtitle id='00:13:25'>that the cells aren't completely in isolation they communicate by means of</subtitle>
<subtitle id='00:13:29'>sending messages to each other and again the way we way we translate that into</subtitle>
<subtitle id='00:13:35'>computer terms is done in a much more</subtitle>
<subtitle id='00:13:40'>restrictive way than biology does it biology generally communicates without</subtitle>
<subtitle id='00:13:44'>wearing who's going to receive I'm going to talk a little bit later about a</subtitle>
<subtitle id='00:13:49'>object-oriented strategy in which messages aren't sent at all they're only</subtitle>
<subtitle id='00:13:54'>received you might think about what an object-oriented system might be like if</subtitle>
<subtitle id='00:13:59'>you never sent a message but objects could receive what would they receive</subtitle>
<subtitle id='00:14:04'>all I could do is receive the translation of this model into machine</subtitle>
<subtitle id='00:14:13'>terms for me 25 years ago or so was that</subtitle>
<subtitle id='00:14:19'>these biological cells acted a lot as though they're on a network you can</subtitle>
<subtitle id='00:14:24'>think of it as a crossbar switch or a</subtitle>
<subtitle id='00:14:28'>Ethernet type network in which every object can send to every other object</subtitle>
<subtitle id='00:14:33'>and each one of these things is a lot like a little computer in fact is very</subtitle>
<subtitle id='00:14:42'>difficult in a good object-oriented system to find out where the hardware</subtitle>
<subtitle id='00:14:47'>stops and the software begins and the</subtitle>
<subtitle id='00:14:52'>this notion of a little computer in the</subtitle>
<subtitle id='00:14:56'>in the large here is something that is worthwhile considering when we think</subtitle>
<subtitle id='00:15:00'>about making very small things now there's a principle in design that</subtitle>
<subtitle id='00:15:07'>people came up with many years ago it's</subtitle>
<subtitle id='00:15:11'>called the basic principle of recursive design and the idea is make the parts</subtitle>
<subtitle id='00:15:16'>have the same power as the whole</subtitle>
<subtitle id='00:15:20'>we know in the factorial example that a</subtitle>
<subtitle id='00:15:25'>recursive program like factorial its</subtitle>
<subtitle id='00:15:29'>charm is it's able to reinvest the</subtitle>
<subtitle id='00:15:33'>conditional branches and so in some sense the program remains as long as</subtitle>
<subtitle id='00:15:39'>that is true the program remains as strong as it was when you entered it</subtitle>
<subtitle id='00:15:43'>because you can always reinter it instead of getting diluted away now</subtitle>
<subtitle id='00:15:49'>another thing that that crossed my mind when I was pondering these ideas back in</subtitle>
<subtitle id='00:15:54'>the 60s was why if that is such a</subtitle>
<subtitle id='00:15:58'>powerful idea why is it that we take a very powerful idea like a computer and</subtitle>
<subtitle id='00:16:04'>dilute it immediately in most programming languages divided by</subtitle>
<subtitle id='00:16:08'>dividing it up into data structures and procedures data structures don't have</subtitle>
<subtitle id='00:16:13'>the same power as a computer they're static can take on marks but they're</subtitle>
<subtitle id='00:16:18'>once once you get a data structure it just sits there procedures don't have</subtitle>
<subtitle id='00:16:24'>the same power as computers because they can't remember state they have to have</subtitle>
<subtitle id='00:16:29'>something additional so what we did in the guise of following standard math</subtitle>
<subtitle id='00:16:34'>mathematical notation in the 50s when Fortran was developed was to mimic</subtitle>
<subtitle id='00:16:40'>standard mathematical notation without thinking about this basic principle of</subtitle>
<subtitle id='00:16:44'>recursive design because people didn't write recursive programs back in the 50s</subtitle>
<subtitle id='00:16:48'>and so the baby is thrown out with the bathwater almost immediately in a</subtitle>
<subtitle id='00:16:52'>standard procedure and data structure language and it occurred to me and other</subtitle>
<subtitle id='00:16:59'>people who are thinking about these ideas back then what if you didn't do</subtitle>
<subtitle id='00:17:04'>that what if the only subdivision you ever made in a programming language was</subtitle>
<subtitle id='00:17:10'>a subdivision of a computer into a computer you're never allowed to</subtitle>
<subtitle id='00:17:15'>subdivide the computer into something that was less than the computer and what</subtitle>
<subtitle id='00:17:19'>does that mean that means that each subdivision has to be something like a</subtitle>
<subtitle id='00:17:23'>black box that has inside of it some</subtitle>
<subtitle id='00:17:27'>mixture of State and process from the</subtitle>
<subtitle id='00:17:31'>outside you can only invoke behavioral attributes</subtitle>
<subtitle id='00:17:36'>rather than invoking method attributes</subtitle>
<subtitle id='00:17:40'>and what I mean by that is this is something that was even in Fortran</subtitle>
<subtitle id='00:17:44'>because the earlier designers of Fortran realized that there is a very funny</subtitle>
<subtitle id='00:17:48'>correspondence between procedural things and data structure things so for</subtitle>
<subtitle id='00:17:52'>instance when you say Si and parentheses</subtitle>
<subtitle id='00:17:56'>30 close parentheses in Fortran you</subtitle>
<subtitle id='00:18:00'>can't tell by looking at that whether you're invoking a function or whether</subtitle>
<subtitle id='00:18:06'>you're accessing an array and that was not accidental back then because of</subtitle>
<subtitle id='00:18:12'>course they thought of arrays as being a kind of a function and they wanted you</subtitle>
<subtitle id='00:18:17'>to be able to write arrays huge tables</subtitle>
<subtitle id='00:18:21'>still done today in order to do</subtitle>
<subtitle id='00:18:25'>functional evaluation very quickly what they didn't realize is that you wanted</subtitle>
<subtitle id='00:18:30'>to be able to trade-off between the two but that notion of just saying sine 30</subtitle>
<subtitle id='00:18:36'>degrees without indicating how its to compete be computed is the essence of</subtitle>
<subtitle id='00:18:41'>the kind of abstraction that that object-oriented programming is all about</subtitle>
<subtitle id='00:18:46'>it's carried very far here by</subtitle>
<subtitle id='00:18:55'>this strong membrane of the object so that what we're dealing with here are</subtitle>
<subtitle id='00:19:00'>behaviors and there are two important</subtitle>
<subtitle id='00:19:04'>implications that had to be worked out early on one of them is that messages in</subtitle>
<subtitle id='00:19:11'>most cases can't be commands or you're</subtitle>
<subtitle id='00:19:16'>violating the notion of the object as being in control now most</subtitle>
<subtitle id='00:19:21'>object-oriented systems today when you do what is called sending a message you</subtitle>
<subtitle id='00:19:26'>are issuing a command Objective C C++</subtitle>
<subtitle id='00:19:30'>even small talk eighty all of those systems a message is actually something</subtitle>
<subtitle id='00:19:38'>very very close to if not identical to a certain kind of procedure call okay but</subtitle>
<subtitle id='00:19:45'>in fact in the original scheme and we can talk about the implications of why</subtitle>
<subtitle id='00:19:49'>this is a good idea later in the original object oriented</subtitle>
<subtitle id='00:19:54'>systems that were so successful messages aren't commands at all what they are are</subtitle>
<subtitle id='00:19:59'>desires I'd like to have this happen just to</subtitle>
<subtitle id='00:20:05'>give you an example of why imagine we have an object masquerading as a</subtitle>
<subtitle id='00:20:10'>critical system file and the question is</subtitle>
<subtitle id='00:20:14'>it should just anybody be able to come up and issue the command to it turn byte</subtitle>
<subtitle id='00:20:20'>5 to 0 now it's done all the time but in</subtitle>
<subtitle id='00:20:25'>fact in an object-oriented system you would like the object to be able to</subtitle>
<subtitle id='00:20:29'>protect itself so that even a person who</subtitle>
<subtitle id='00:20:33'>has a pointer to it even a person who has the knowledge of which command is</subtitle>
<subtitle id='00:20:38'>the right command that both of those do</subtitle>
<subtitle id='00:20:42'>not imply that you have permission to actually change that file so in the when</subtitle>
<subtitle id='00:20:49'>I talk about an object-oriented system I mean an object in which the worst you</subtitle>
<subtitle id='00:20:55'>can do to an object is to simply indicate to it that you would like it to</subtitle>
<subtitle id='00:21:00'>do something for you and the best that can happen is it will do that the worst</subtitle>
<subtitle id='00:21:07'>that can happen to it internally as it will simply refuse it may put you may take your name</subtitle>
<subtitle id='00:21:13'>and give it to the principal later if</subtitle>
<subtitle id='00:21:17'>you've done something wrong but so this notion of absolute control that messages</subtitle>
<subtitle id='00:21:23'>can't be commands and the other one is</subtitle>
<subtitle id='00:21:27'>because the object is no longer a data structure in any sense that we regard it</subtitle>
<subtitle id='00:21:32'>that assignment is something that can't</subtitle>
<subtitle id='00:21:37'>be done from the outside either so the assignment statement has to go away in</subtitle>
<subtitle id='00:21:42'>the form that we know it as an irrevocable change to a variable or a</subtitle>
<subtitle id='00:21:49'>slot in a data structure an assignment has to be changed by something that we</subtitle>
<subtitle id='00:21:53'>can think of as being advice or influence so again this notion of</subtitle>
<subtitle id='00:22:01'>getting an object to to change its state is something that we normally don't do</subtitle>
<subtitle id='00:22:07'>in object-oriented programming because normally in object-oriented programming</subtitle>
<subtitle id='00:22:11'>we are not simply trying to imitate data structures now to be a data structure is</subtitle>
<subtitle id='00:22:17'>that thing that if you send it to</subtitle>
<subtitle id='00:22:21'>somebody else you're giving them permission to change it that's what I</subtitle>
<subtitle id='00:22:25'>mean by a data structure so it's clear that some of the things that we call</subtitle>
<subtitle id='00:22:29'>data structures in normal parlance in a</subtitle>
<subtitle id='00:22:34'>system with an operating system that offers some protection are not strictly</subtitle>
<subtitle id='00:22:39'>classical data structures by that means certain files usually have protections</subtitle>
<subtitle id='00:22:44'>on them so that in a good operating system when we send a file from us to</subtitle>
<subtitle id='00:22:51'>somebody else we are not can conveying to that person</subtitle>
<subtitle id='00:22:55'>the same level of protection necessarily that we have been granted so in a good</subtitle>
<subtitle id='00:23:01'>operating system this is this may be an operating system that you've never seen</subtitle>
<subtitle id='00:23:05'>but there there have been operating systems in the past there exist</subtitle>
<subtitle id='00:23:09'>operating systems now so that if you have a certain set of permissions for a</subtitle>
<subtitle id='00:23:14'>file a and you wish to give it this file</subtitle>
<subtitle id='00:23:19'>to your friend suppose you have the the magic permission to change the any</subtitle>
<subtitle id='00:23:25'>byte in the system file because you're a honcho then you might wonder should I be</subtitle>
<subtitle id='00:23:31'>able to pass on those permissions to the</subtitle>
<subtitle id='00:23:36'>next person that I give this file to the answer to good operating system is no</subtitle>
<subtitle id='00:23:41'>each person should get their own permission separately and when they</subtitle>
<subtitle id='00:23:46'>receive this file a it's their permissions that are granted by the</subtitle>
<subtitle id='00:23:51'>operating system that obtain not the permissions passed on to them by</subtitle>
<subtitle id='00:23:56'>somebody who had the file before so you can think of taking this desperately</subtitle>
<subtitle id='00:24:02'>important file passing it along and when</subtitle>
<subtitle id='00:24:08'>it goes to somebody who is less to be trusted with it they have fewer</subtitle>
<subtitle id='00:24:12'>permissions on that there are fewer things that they can do with it and then</subtitle>
<subtitle id='00:24:16'>they passed it on to somebody again that may go back to a trusted person that</subtitle>
<subtitle id='00:24:21'>person should be able to reintroduce</subtitle>
<subtitle id='00:24:27'>that is called capability protection and</subtitle>
<subtitle id='00:24:31'>capability protection is again another one of these old ideas from the 60s</subtitle>
<subtitle id='00:24:35'>intertwined in a very strong way with</subtitle>
<subtitle id='00:24:40'>object-oriented design that is now coming back capability is simply a</subtitle>
<subtitle id='00:24:45'>technique for protecting objects in a</subtitle>
<subtitle id='00:24:49'>stronger way than normal digital computers allow them to be done and</subtitle>
<subtitle id='00:24:54'>again at the end of the at the towards the end of the talk we'll talk a little</subtitle>
<subtitle id='00:24:58'>bit about this so to me there are lots</subtitle>
<subtitle id='00:25:04'>of different ways of talking about objects but probably 90% of the reason</subtitle>
<subtitle id='00:25:10'>to me for dealing with objects at all has to do with their abilities to</subtitle>
<subtitle id='00:25:15'>protect in various ways protect by</subtitle>
<subtitle id='00:25:20'>encapsulating various kinds of things almost always state less often control</subtitle>
<subtitle id='00:25:27'>is encapsulated and so forth then about</subtitle>
<subtitle id='00:25:31'>10 percent of the use of object-oriented programming to</subtitle>
<subtitle id='00:25:35'>has to do with its ability in whispering</subtitle>
<subtitle id='00:25:39'>to you how you might design a system better and just one more note about that</subtitle>
<subtitle id='00:25:44'>before I get started on the on the talk proper and that is that the way objects</subtitle>
<subtitle id='00:25:52'>are used today is a little bit confusing because they're intertwined with a</subtitle>
<subtitle id='00:25:57'>another set of ideas that came out of the 70s that are very similar</subtitle>
<subtitle id='00:26:03'>particularly in implementation these days and that's what's called data</subtitle>
<subtitle id='00:26:07'>abstraction how many people are familiar with data abstraction as a idea okay so</subtitle>
<subtitle id='00:26:13'>data abstraction looks a lot like object-oriented programming but its</subtitle>
<subtitle id='00:26:17'>intent is different the intent of data abstraction is to take a system that</subtitle>
<subtitle id='00:26:24'>you're familiar with like Pascal or Fortran that is starting to run into</subtitle>
<subtitle id='00:26:30'>difficulties of various kinds difficult is usually a representational ones I</subtitle>
<subtitle id='00:26:36'>think everybody's had the experience programming in a language with data</subtitle>
<subtitle id='00:26:41'>structures you get this big system done you decide you need to change your</subtitle>
<subtitle id='00:26:46'>representation and the next thing you know you're hunting down all of the</subtitle>
<subtitle id='00:26:51'>procedures that think they knew about the old representation and the rule of</subtitle>
<subtitle id='00:26:55'>the universe is that there's always one or two that you don't find so you slide</subtitle>
<subtitle id='00:27:01'>in the new representation and a couple of months later one of those procedures</subtitle>
<subtitle id='00:27:06'>is invoked and all of a sudden you have a crash and people wonder why the answer</subtitle>
<subtitle id='00:27:11'>is the critical knowledge has actually</subtitle>
<subtitle id='00:27:15'>been spread out in such a way that it can't be recovered it's like what you</subtitle>
<subtitle id='00:27:19'>have to do after you do a multiplication in order to recover the the operands you</subtitle>
<subtitle id='00:27:24'>have to do much more work like the difference between differentiation and</subtitle>
<subtitle id='00:27:28'>integration the same thing is true is once you've lost information in a</subtitle>
<subtitle id='00:27:32'>century in a system once the entropy has</subtitle>
<subtitle id='00:27:36'>gone up then it's very hard to get it back so one of the things that you try</subtitle>
<subtitle id='00:27:42'>and do with objects is to try and maintain the</subtitle>
<subtitle id='00:27:46'>as much informational content as you possibly can in a smaller place as possible now data</subtitle>
<subtitle id='00:27:52'>abstraction techniques use a similar way of wrapping an envelope around a data</subtitle>
<subtitle id='00:27:59'>structure and invoke operations by means of procedures in order to try and get it</subtitle>
<subtitle id='00:28:07'>to be a little bit more representation independent the difference though ADA</subtitle>
<subtitle id='00:28:12'>for instance is a language that is a data abstraction language is not an</subtitle>
<subtitle id='00:28:18'>object-oriented language and even the the people who actually understand ADA</subtitle>
<subtitle id='00:28:22'>don't claim that but you can do certain kinds of things that are now today</subtitle>
<subtitle id='00:28:27'>called object-oriented in Ada so this</subtitle>
<subtitle id='00:28:32'>envelope of procedures is wrapped around the data structure in an effort to</subtitle>
<subtitle id='00:28:37'>protect it but then what happens is that this new structure that's been created</subtitle>
<subtitle id='00:28:42'>is then treated as a data structure by all the rest of the program the result</subtitle>
<subtitle id='00:28:48'>is in particularly in ada is that the</subtitle>
<subtitle id='00:28:53'>programs are not small the programs aren't any smaller than they were before</subtitle>
<subtitle id='00:28:59'>and one of the hallmarks of object-oriented programming if you have any sense of whether you're doing it</subtitle>
<subtitle id='00:29:05'>right or not is that the programs are remarkably smaller because there's a way</subtitle>
<subtitle id='00:29:11'>of using the design that is not simply</subtitle>
<subtitle id='00:29:15'>imitating a bad old idea which is data structures and trying to shore it up by</subtitle>
<subtitle id='00:29:20'>putting it in an orthotic brace but in fact to go beyond the notion of data</subtitle>
<subtitle id='00:29:25'>structures so for instance in in a NATO way of of doing object-oriented</subtitle>
<subtitle id='00:29:30'>programming one typically comes out with</subtitle>
<subtitle id='00:29:35'>something that looks very much like a data structure it has fields that are to</subtitle>
<subtitle id='00:29:39'>be written to it has fields that data is to be taken out of the structure is</subtitle>
<subtitle id='00:29:45'>static there's no actual process going on and it's essentially a slightly more</subtitle>
<subtitle id='00:29:52'>abstract way of doing data typically in an object a good object will not</subtitle>
<subtitle id='00:29:57'>actually permit you to write assignment statements to it at</subtitle>
<subtitle id='00:30:02'>all because an object generally will not</subtitle>
<subtitle id='00:30:07'>look at all like a data structure just to give you an example we can contrast a</subtitle>
<subtitle id='00:30:12'>personnel record as it might be done in</subtitle>
<subtitle id='00:30:16'>Ada in which we still wind up with fields as we had them before some of the</subtitle>
<subtitle id='00:30:23'>fields might be a little bit more connected but it's still a large thing</subtitle>
<subtitle id='00:30:27'>it's still passed around as a passive object we could contrast that with an</subtitle>
<subtitle id='00:30:32'>object-oriented approach with which would be to try and turn the personnel record into something much more like the</subtitle>
<subtitle id='00:30:38'>like a real person in other words this personnel record instead of sitting</subtitle>
<subtitle id='00:30:45'>there on a file waiting to be manipulated would actually be trying to participate actively in some sort of</subtitle>
<subtitle id='00:30:51'>simulation instead of changing the person's age from the outside the way</subtitle>
<subtitle id='00:30:58'>you might do in a data record the age of the person would change dynamically as</subtitle>
<subtitle id='00:31:03'>the birthday was passed because there was something in this object that was</subtitle>
<subtitle id='00:31:07'>actively looking at the clock actively running in some sense the notion of</subtitle>
<subtitle id='00:31:14'>being able to edit the object from the outside would be much less in the sense</subtitle>
<subtitle id='00:31:19'>of editing the actual fields so objects even in a in a programming language in</subtitle>
<subtitle id='00:31:25'>which everything is an object like small talk objects tend to be larger things</subtitle>
<subtitle id='00:31:30'>than data structures they tend to be</subtitle>
<subtitle id='00:31:34'>components active machines that fit</subtitle>
<subtitle id='00:31:39'>together with other active machines to make a new kind of structure just to</subtitle>
<subtitle id='00:31:43'>give you an example of a modern attempt</subtitle>
<subtitle id='00:31:47'>at large scale object-oriented programming which hasn't been done very</subtitle>
<subtitle id='00:31:51'>much for a long time the largest object-oriented system was small talk</subtitle>
<subtitle id='00:31:55'>zone system which was even though it had</subtitle>
<subtitle id='00:32:00'>its own user interface and its own operating system and its own sets of</subtitle>
<subtitle id='00:32:07'>editors and facilities and file system</subtitle>
<subtitle id='00:32:11'>and every other kind of thing the small talk ad system that is distributed by park play systems</subtitle>
<subtitle id='00:32:15'>for instance is only about 40,000 lines of code which to me is is 10</subtitle>
<subtitle id='00:32:22'>approximately 4 to 10 times as large as it actually needs to be it's actually</subtitle>
<subtitle id='00:32:27'>kind of junky in various ways but when</subtitle>
<subtitle id='00:32:32'>you consider that the UNIX kernel it's alone is 400,000 lines of C and that is</subtitle>
<subtitle id='00:32:37'>thought to be a rather small kernel in the operating system domain you can see</subtitle>
<subtitle id='00:32:41'>that most object-oriented programming historically the programs have been tiny</subtitle>
<subtitle id='00:32:48'>the all of the stuff that we did at Parc that led to the Macintosh could be</subtitle>
<subtitle id='00:32:54'>summed up this includes the equivalent of about 15 different Macintosh</subtitle>
<subtitle id='00:32:58'>applications including mac draw and mac paint and all of those things were</subtitle>
<subtitle id='00:33:03'>summed up by approximately 175 pages of</subtitle>
<subtitle id='00:33:08'>code or approximately 8,000 lines of</subtitle>
<subtitle id='00:33:13'>code that included the operating system the user interface and everything these</subtitle>
<subtitle id='00:33:18'>programs are tiny when they're done right because of that people have been</subtitle>
<subtitle id='00:33:23'>very suspicious of them in the world for instance that you come from you know</subtitle>
<subtitle id='00:33:28'>does this idea really scale is it just for toy problems and so forth the most</subtitle>
<subtitle id='00:33:34'>recent example of object-oriented programming in the large that I know has</subtitle>
<subtitle id='00:33:39'>one done by Arthur Anderson consulting at the Brooklyn Union gas company over</subtitle>
<subtitle id='00:33:44'>the last year now Arthur Anderson I don't know how large the jobs typically</subtitle>
<subtitle id='00:33:49'>are at McDonnell Douglas but Arthur Andersen consulting typically and I</subtitle>
<subtitle id='00:33:55'>think they do some work for McDonnell Douglas but typically when they get to</subtitle>
<subtitle id='00:34:00'>work on a job their clients have already failed a couple of times and implementing it they're usually called</subtitle>
<subtitle id='00:34:06'>in at the last moment they charge twenty</subtitle>
<subtitle id='00:34:11'>to fifty million dollars a pop for one</subtitle>
<subtitle id='00:34:15'>of these jobs and their jobs typically run to about one and a half million to</subtitle>
<subtitle id='00:34:19'>two million lines of COBOL this this is</subtitle>
<subtitle id='00:34:23'>done over a period of about a year and a half to two years by a highly trained group of</subtitle>
<subtitle id='00:34:28'>people I think of as technological Marines they have a very rigorous</subtitle>
<subtitle id='00:34:37'>high-spirited training facility called st. Charles they have a approximately</subtitle>
<subtitle id='00:34:41'>27,000 people who do this kind of work</subtitle>
<subtitle id='00:34:45'>and it's a fascinating fascinating set up I'm on their technical advisory board</subtitle>
<subtitle id='00:34:49'>and I got on the board partly just because I was interested in the culture</subtitle>
<subtitle id='00:34:53'>of this particular company I was really surprised that given how successful</subtitle>
<subtitle id='00:34:58'>they've been that they have been shifting their entire set of operations</subtitle>
<subtitle id='00:35:03'>over to objects over the last five years or so it's an enormous change for them</subtitle>
<subtitle id='00:35:08'>because they have it's not the change in</subtitle>
<subtitle id='00:35:12'>going from a non object-oriented language to an object-oriented language the change of going from one kind of</subtitle>
<subtitle id='00:35:18'>culture to another kind of culture it's a change that as Koon mentioned about</subtitle>
<subtitle id='00:35:22'>paradigms the reason the paradigm shifts take 25 years or more in science is in</subtitle>
<subtitle id='00:35:28'>order to have a paradigm shift in science you generally have to let the old physicists die off once once people</subtitle>
<subtitle id='00:35:35'>have learned a technique and have gotten comfortable with it is extremely</subtitle>
<subtitle id='00:35:39'>difficult for them to go to something else the Macintosh user interface in its</subtitle>
<subtitle id='00:35:43'>early stages had that difficult people had gotten so good with function keys</subtitle>
<subtitle id='00:35:48'>that they actually felt diminished by</subtitle>
<subtitle id='00:35:53'>using the mouse even after was shown to them that the mouse is four times more</subtitle>
<subtitle id='00:35:58'>efficient in speed over what they've been doing with the function keys it</subtitle>
<subtitle id='00:36:03'>didn't seem that way to them because they've gotten so adroit with it and the</subtitle>
<subtitle id='00:36:07'>same thing is true with any technique that people use so Arthur Andersen has</subtitle>
<subtitle id='00:36:12'>done a number of different pilot projects but last year they started the</subtitle>
<subtitle id='00:36:17'>first large implementation this is a project that was a reimplementation of a</subtitle>
<subtitle id='00:36:24'>system that had been done some years ago and it was originally designed to be</subtitle>
<subtitle id='00:36:29'>done in the standard Arthur Anderson case tools and the estimate was 1.7</subtitle>
<subtitle id='00:36:35'>million lines of COBOL and approximately 2 to</subtitle>
<subtitle id='00:36:39'>two and a half years of implementation time to do this enormous system which is</subtitle>
<subtitle id='00:36:44'>both both an accounting system and a management information system and as an</subtitle>
<subtitle id='00:36:50'>experiment they decided to left a New York group which had been the pioneers</subtitle>
<subtitle id='00:36:54'>in object-oriented programming do a</subtitle>
<subtitle id='00:36:58'>implementation using object-oriented techniques now of course they didn't</subtitle>
<subtitle id='00:37:02'>have an object-oriented language to work with for their end result this was to be</subtitle>
<subtitle id='00:37:07'>done on IBM mainframes 30 90s there are</subtitle>
<subtitle id='00:37:12'>no object-oriented languages extant on</subtitle>
<subtitle id='00:37:18'>the 30 90 so they did a trial implementation to test out the design in</subtitle>
<subtitle id='00:37:24'>small talk taking a few months to do it and then wrote a set of library routines</subtitle>
<subtitle id='00:37:31'>and some pre-processing macros for PL 1 and then we implemented this project</subtitle>
<subtitle id='00:37:39'>with about 10 programmers in PL 1 so the</subtitle>
<subtitle id='00:37:43'>results of that are now in the minor</subtitle>
<subtitle id='00:37:47'>interesting thing was that they got done about 6 months early the major</subtitle>
<subtitle id='00:37:53'>interesting thing was that the amount of code that actually had to be written to</subtitle>
<subtitle id='00:37:57'>do this Amandla to 150,000 lines of this</subtitle>
<subtitle id='00:38:01'>library is PL 1 as opposed to the 1.7</subtitle>
<subtitle id='00:38:05'>million lines of COBOL that their estimates had done before so this is a</subtitle>
<subtitle id='00:38:11'>factor of 11 less code and from their standpoint the six months was down in</subtitle>
<subtitle id='00:38:16'>the noise because the the months that they're interested in are the 5 or 6</subtitle>
<subtitle id='00:38:21'>years of maintaining the code from then on and being able to reuse those modules</subtitle>
<subtitle id='00:38:27'>as they are going to be able to on other 3090 implementation so in some sense the</subtitle>
<subtitle id='00:38:34'>the fact that you can program faster that you're you can save time and so</subtitle>
<subtitle id='00:38:40'>forth in object-oriented programming in in the larger world is not nearly as</subtitle>
<subtitle id='00:38:45'>interesting it as it is in research and research basically the ability to do</subtitle>
<subtitle id='00:38:49'>quick prototyping dominates almost everything else</subtitle>
<subtitle id='00:38:53'>in the large world the world that you come from the world that Arthur Andersen</subtitle>
<subtitle id='00:38:57'>is in quick prototyping is something they'd like to do they're starting to do it but it's not nearly as important as</subtitle>
<subtitle id='00:39:02'>maintainability reusability is the</subtitle>
<subtitle id='00:39:07'>second thing if they can reuse a module as a component in some other system then</subtitle>
<subtitle id='00:39:14'>they have saved themselves an enormous amount not of time although they have</subtitle>
<subtitle id='00:39:21'>certainly done that but to them it's not time but it's designer skills the thing</subtitle>
<subtitle id='00:39:28'>that all large companies are weak on is having enough designers to go around</subtitle>
<subtitle id='00:39:33'>they're usually plenty of people to write code but the designers are few and</subtitle>
<subtitle id='00:39:38'>far between and this notion that a successful design can actually be moved</subtitle>
<subtitle id='00:39:43'>from one place to another in components is something that literally drives the</subtitle>
<subtitle id='00:39:48'>Arthur Andersen people crazy with joy to to think about so they have now come up</subtitle>
<subtitle id='00:39:52'>with an object-oriented repository and are starting to craft rather large</subtitle>
<subtitle id='00:39:59'>useful objects that can be used as standard components and building blocks</subtitle>
<subtitle id='00:40:03'>in various systems and we'll talk a little bit later about how one goes</subtitle>
<subtitle id='00:40:07'>about to me this is what object-oriented programming is about it's not saving</subtitle>
<subtitle id='00:40:13'>data structures from itself it's not making a slightly fancier data structure</subtitle>
<subtitle id='00:40:18'>it's not even making a data structure that can implement certain kinds of constraints within itself and so forth</subtitle>
<subtitle id='00:40:24'>it's thinking of those objects as independent machines going back to this</subtitle>
<subtitle id='00:40:30'>whole biological notion that it's one thing to build cells and it's another</subtitle>
<subtitle id='00:40:35'>thing to build tissues and for people</subtitle>
<subtitle id='00:40:40'>who are just starting out in object-oriented programming they're usually thrilled that they can build cells but the real goal is to be had</subtitle>
<subtitle id='00:40:46'>when you move from cells to thinking about what are the tissues what are the</subtitle>
<subtitle id='00:40:50'>conglomerations of these atomic style objects into components that if you were</subtitle>
<subtitle id='00:40:57'>to have three or four hundred of them in a repository usable by any programmer</subtitle>
<subtitle id='00:41:04'>what would you be able to build could you be able to Tinkertoy things</subtitle>
<subtitle id='00:41:08'>together could end-user programmers be</subtitle>
<subtitle id='00:41:12'>able to do a considerable amount of the programming and retailer and so forth so</subtitle>
<subtitle id='00:41:18'>the real change if there is one I think</subtitle>
<subtitle id='00:41:22'>I think it's coming faster than we think that object-oriented programming is</subtitle>
<subtitle id='00:41:26'>going to bring along is actually both a change in the way professional</subtitle>
<subtitle id='00:41:31'>programmers do their work but even more so a change in the way these</subtitle>
<subtitle id='00:41:35'>applications are designed another example for instance at Apple now we</subtitle>
<subtitle id='00:41:40'>design all of the applications that we do as though they are going to be</subtitle>
<subtitle id='00:41:46'>actually tailored not completed but</subtitle>
<subtitle id='00:41:50'>tailored by an end-user a person who has</subtitle>
<subtitle id='00:41:55'>programmed almost not at all person who's used HyperCard a few times</subtitle>
<subtitle id='00:41:59'>so this is a really big change and it's</subtitle>
<subtitle id='00:42:03'>something that has been talked about for 20 years or more but it's something that</subtitle>
<subtitle id='00:42:08'>just now is possible to actually do what does it mean well it means what you'd</subtitle>
<subtitle id='00:42:13'>like when you get an application from somebody is to be able to use it right</subtitle>
<subtitle id='00:42:19'>out of the box read them the manual understand what it is don't have to sit</subtitle>
<subtitle id='00:42:27'>down and think about it as a kit or anything but just use it the way you're used to using it now it's a temporary</subtitle>
<subtitle id='00:42:32'>solution to some set of problems you have right now also you wouldn't be using it but a month later your old</subtitle>
<subtitle id='00:42:39'>attitude about this ad this application has changed completely month later now</subtitle>
<subtitle id='00:42:44'>you're saying boy I wish this thing could do this and I wish this thing could do this everybody does that person</subtitle>
<subtitle id='00:42:50'>who's never program before is only used the computer for a couple of weeks after</subtitle>
<subtitle id='00:42:55'>a couple of weeks they'll say boy I wish this thing could do this and I wish it could do that and that's the point where</subtitle>
<subtitle id='00:43:00'>you'd like to hit the hood latch button on the application and open it up and</subtitle>
<subtitle id='00:43:05'>see something in there that was comprehensible right now if you open an</subtitle>
<subtitle id='00:43:10'>application on the Macintosh you open it up it's sort of like looking into the</subtitle>
<subtitle id='00:43:14'>hood of a Mercedes Benz or something there's this mass of tubing and if the</subtitle>
<subtitle id='00:43:19'>thing had a carburetor you find it because it's a mass of spaghetti</subtitle>
<subtitle id='00:43:23'>mostly machine code on desktop micros but doesn't matter whether it's machine</subtitle>
<subtitle id='00:43:28'>code or Fortran it's a mess and on the</subtitle>
<subtitle id='00:43:33'>other hand what the user wants to see when they open it up is something that looks like a Model T they want to see a</subtitle>
<subtitle id='00:43:39'>schematic even if there's a Ferrari underneath the Model T they want to see</subtitle>
<subtitle id='00:43:44'>a Model T they want to see a schematic engine of what makes that application</subtitle>
<subtitle id='00:43:51'>tick because they've already got an intuitive notion about how that works and then they would like to be able to</subtitle>
<subtitle id='00:43:56'>make changes at the level of that schematic engine there are a bunch of</subtitle>
<subtitle id='00:44:01'>applications you can buy for the Macintosh now in which that's possible</subtitle>
<subtitle id='00:44:05'>an example is focal point and most many</subtitle>
<subtitle id='00:44:09'>other applications written in hyper card because hypercard is a an object-oriented language set up so that</subtitle>
<subtitle id='00:44:16'>professional applications programmers can give you not just architectures not</subtitle>
<subtitle id='00:44:21'>just a kit but working architectures working kids and then after you've used</subtitle>
<subtitle id='00:44:26'>them for several months you can make the change that's going to change the whole</subtitle>
<subtitle id='00:44:30'>way we go about designing things professional programmers won't be</subtitle>
<subtitle id='00:44:34'>designing programs for each other or F at its worst professional programmers</subtitle>
<subtitle id='00:44:39'>tend to design programs that will keep them in job security there's a class of</subtitle>
<subtitle id='00:44:46'>programmer who delights in the obscure they love the fact that they are the</subtitle>
<subtitle id='00:44:50'>only ones that can understand how this program works and there's a maxim that</subtitle>
<subtitle id='00:44:55'>says if you're the only one who understands how it works you don't understand how it works and so progress</subtitle>
<subtitle id='00:45:02'>is isn't to be made there so so I think</subtitle>
<subtitle id='00:45:06'>I'm going to go into the the give you an</subtitle>
<subtitle id='00:45:11'>idea about where some of these ideas came from the one thing I think you may</subtitle>
<subtitle id='00:45:15'>be a little bit surprised to add is some of the earliest object-oriented ideas</subtitle>
<subtitle id='00:45:19'>were some of the most sophisticated and it will be revisiting them in the next</subtitle>
<subtitle id='00:45:24'>five and ten years to come one of the reasons for this is that because you</subtitle>
<subtitle id='00:45:29'>couldn't make money in computing in the 60s many of the people who</subtitle>
<subtitle id='00:45:34'>had ideas about how computing should be done in the 60s had extremely pure</subtitle>
<subtitle id='00:45:38'>conceptions those conceptions are</subtitle>
<subtitle id='00:45:42'>powerful yet today and it's worthwhile showing you a few of them</subtitle>
<subtitle id='00:46:01'>so just just as a reference point</subtitle>
<subtitle id='00:46:09'>I like I always like to start off with this slide because this is my vote for</subtitle>
<subtitle id='00:46:18'>the world's first personal computer this</subtitle>
<subtitle id='00:46:23'>picture was taken at Lincoln labs in 1962 summer of 1962 and this is a</subtitle>
<subtitle id='00:46:29'>machine called the link and it's</subtitle>
<subtitle id='00:46:33'>especially appropriate to mention here since the person who invented this machine West Clarke had a research</subtitle>
<subtitle id='00:46:38'>project at Washington University for many years</subtitle>
<subtitle id='00:46:43'>sponsored by ARPA those things that look like Dec tapes over on the side he</subtitle>
<subtitle id='00:46:48'>actually invented they were called link type tapes originally and this is kind</subtitle>
<subtitle id='00:46:53'>of a metaphor for our talk which is the</subtitle>
<subtitle id='00:46:59'>best that Dec could do with these ideas that came out of Lincoln labs as well</subtitle>
<subtitle id='00:47:04'>when Dec saw this machine in the early 60s it said boy what a great way of</subtitle>
<subtitle id='00:47:08'>making a small mainframe and it immediately adapted the the architecture</subtitle>
<subtitle id='00:47:15'>of the link to make many computers but Dec said well people aren't used to</subtitle>
<subtitle id='00:47:21'>looking at displays let's make that an option so he took the display away and</subtitle>
<subtitle id='00:47:27'>people didn't understand what was</subtitle>
<subtitle id='00:47:32'>actually on the link tapes some obscure stuff so they said well let's put files</subtitle>
<subtitle id='00:47:37'>on the link tape so I'll call him Dec tapes and out of this machine Dec was</subtitle>
<subtitle id='00:47:44'>able to come up with the astounding idea of the mini computer whereas in fact about 2,000 of these were built in the</subtitle>
<subtitle id='00:47:51'>60s and an astounding as far as I've been able to determine is an astounding</subtitle>
<subtitle id='00:47:55'>900 of them seemed to be still working today now they were designed for</subtitle>
<subtitle id='00:48:02'>biomedical labs for technicians who</subtitle>
<subtitle id='00:48:07'>needed to do their own programming and needed to do real-time experiments and</subtitle>
<subtitle id='00:48:11'>it was an almost perfect machine by the way what was on those original link</subtitle>
<subtitle id='00:48:16'>tapes what was on there were the pages of the virtual memory this first personal computer</subtitle>
<subtitle id='00:48:21'>had it's very hard to go out today and</subtitle>
<subtitle id='00:48:25'>buy a personal computer that has a real</subtitle>
<subtitle id='00:48:30'>virtual memory this machine had it back in 1962 so as an excellent idea but like</subtitle>
<subtitle id='00:48:36'>many things thought of it it actually</subtitle>
<subtitle id='00:48:40'>was so far ahead of its time that it took another decade or so for people to</subtitle>
<subtitle id='00:48:44'>catch up to it</subtitle>
<subtitle id='00:48:48'>one of the very first object-oriented software systems and one that's I think</subtitle>
<subtitle id='00:48:52'>a particularly in this talk is Ivan Sutherland sketchpad which is also done</subtitle>
<subtitle id='00:48:58'>at Lincoln labs on the tx2 computer which was the last computer in America</subtitle>
<subtitle id='00:49:04'>large enough to have its own roof and in fact was it was about four times the</subtitle>
<subtitle id='00:49:10'>size of this room and every Thursday they would take it down and change about</subtitle>
<subtitle id='00:49:16'>10% of it because they were always</subtitle>
<subtitle id='00:49:20'>putting new things it had some of the earliest core memory ever devised and</subtitle>
<subtitle id='00:49:25'>it's quite a remarkable machine for its day it was used as a single user machine</subtitle>
<subtitle id='00:49:29'>by Ivan Sutherland to invent sketchpad</subtitle>
<subtitle id='00:49:33'>and you see him here he's working with a</subtitle>
<subtitle id='00:49:37'>bridge truss sketchpad is very difficult to appreciate and just by looking at</subtitle>
<subtitle id='00:49:44'>slides so I thought I would show you a videotape of it in operation so if we</subtitle>
<subtitle id='00:49:48'>could run the first videotape take a</subtitle>
<subtitle id='00:49:54'>look and see what this again is the summer of 62 is tape number one stop</subtitle>
<subtitle id='00:50:08'>could you we I thought that was rewound could you rewind that please</subtitle>
<subtitle id='00:50:20'>and then show it</subtitle>
<subtitle id='00:51:02'>now back then they didn't really have computer displays as we know them today</subtitle>
<subtitle id='00:51:06'>so that tx2 here is actually simulating the lines by drawing dots rubber band</subtitle>
<subtitle id='00:51:13'>technique that you've seen before now here's something that I even invented which is he's pointing at the edges and</subtitle>
<subtitle id='00:51:19'>telling sketchpad he wants them all to be mutually perpendicular and sketchpad</subtitle>
<subtitle id='00:51:25'>just solved that problem we see the sketch pad is the first system to have a</subtitle>
<subtitle id='00:51:29'>window the virtual paper he's drawing on</subtitle>
<subtitle id='00:51:34'>is about a third of a mile on a side</subtitle>
<subtitle id='00:51:38'>here the constraint was make the lines parallel now the constraint is</subtitle>
<subtitle id='00:51:43'>collinearity so sketch pad wasn't just</subtitle>
<subtitle id='00:51:48'>the first graphic system was also the first non procedural programming system</subtitle>
<subtitle id='00:51:56'>so everything is controlled by non</subtitle>
<subtitle id='00:52:01'>procedurally giving goals that the system has to figure out here he's</subtitle>
<subtitle id='00:52:05'>making the guidelines invisible to get some dashed lines</subtitle>
<subtitle id='00:52:16'>so he's made himself a flange now he wants to make a rivet and this is why it</subtitle>
<subtitle id='00:52:21'>was called a sketchpad that you didn't</subtitle>
<subtitle id='00:52:25'>want to have to be precise he wanted to be able to just sort of sketch things</subtitle>
<subtitle id='00:52:29'>he's gonna use that as the center for an arc and now he's going to again point to</subtitle>
<subtitle id='00:52:39'>those and say make them mutually perpendicular that pulls the center</subtitle>
<subtitle id='00:52:43'>which pulls the arc which makes it symmetric which makes the rivet because</subtitle>
<subtitle id='00:52:48'>of the way that program is implemented you can actually see it solve the</subtitle>
<subtitle id='00:52:52'>problem there's actually quite</subtitle>
<subtitle id='00:52:58'>sophisticated this is a nonlinear problem that's actually solving</subtitle>
<subtitle id='00:53:12'>so no matter how he distorts it it comes up with the same general shape and he</subtitle>
<subtitle id='00:53:16'>could constrain the ratios of the lengths if he wanted to now what he's</subtitle>
<subtitle id='00:53:23'>been working on there was actually what we today would call a class he called it a master and this is an instance of that</subtitle>
<subtitle id='00:53:31'>Rivet can make it larger or smaller</subtitle>
<subtitle id='00:53:45'>so he wants to latch it into the flange here you can see that this program</subtitle>
<subtitle id='00:53:52'>rapidly led to better display designs</subtitle>
<subtitle id='00:53:59'>these are other instances of the rivet and now he goes back to the master and</subtitle>
<subtitle id='00:54:07'>says well let's make those guidelines invisible so it looks more like a rivet and we see that the instances</subtitle>
<subtitle id='00:54:12'>dynamically feel that change so these</subtitle>
<subtitle id='00:54:16'>are not copies but actually dynamic instances</subtitle>
<subtitle id='00:54:34'>okay and now he shows that any constructed thing can be a master so he</subtitle>
<subtitle id='00:54:41'>had made the plan for the rivet into a master now he's pulling instances from it and rotating them and changing them</subtitle>
<subtitle id='00:54:47'>and so forth</subtitle>
<subtitle id='00:54:58'>okay if you stop that tape please so</subtitle>
<subtitle id='00:55:03'>sketchpad even today is an amazing program you can't buy a graphics system</subtitle>
<subtitle id='00:55:09'>that is nearly as as good today in the</subtitle>
<subtitle id='00:55:14'>sense of it being a comprehensive system for allowing you to set up problems</subtitle>
<subtitle id='00:55:23'>allowing you to solve problems its implementation not just its appearance</subtitle>
<subtitle id='00:55:28'>was also object oriented and the style</subtitle>
<subtitle id='00:55:33'>was something that Ivan settlin came up pretty much on his own because of the</subtitle>
<subtitle id='00:55:39'>difficulty in dealing with many different kinds of objects and having</subtitle>
<subtitle id='00:55:44'>them solve constraints and being able to make pictures for them of themselves and</subtitle>
<subtitle id='00:55:49'>so forth so he got interested in this idea that each object could actually</subtitle>
<subtitle id='00:55:53'>have its own drawing procedure embedded in it and all you had to do is be able</subtitle>
<subtitle id='00:55:59'>to send the message draw to any of the objects and it would invoke the correct</subtitle>
<subtitle id='00:56:04'>procedure although would be a different procedure each time and the same notions</subtitle>
<subtitle id='00:56:08'>were later used for constraints now I</subtitle>
<subtitle id='00:56:13'>once I asked to Ivan I said Ivan how how</subtitle>
<subtitle id='00:56:17'>is it possible for you to in one year just by yourself come up with the</subtitle>
<subtitle id='00:56:22'>world's first graphics system the first non procedural programming system and</subtitle>
<subtitle id='00:56:27'>the first object-oriented software system and he said to me well I didn't</subtitle>
<subtitle id='00:56:31'>know it was hard</subtitle>
<subtitle id='00:56:35'>fortunately didn't and actually it has it has barely been improved on since</subtitle>
<subtitle id='00:56:39'>there have been some improvements since the system called thing lab done at park</subtitle>
<subtitle id='00:56:45'>about a decade ago or so was an improvement on it this whole area of</subtitle>
<subtitle id='00:56:51'>constraint driven object-oriented</subtitle>
<subtitle id='00:56:55'>programming is something that is a hot topic in research right now and I think</subtitle>
<subtitle id='00:56:59'>for the first time in twenty years is actually going to yield some fruit over</subtitle>
<subtitle id='00:57:03'>the next five to ten years the reason is is that people who do mechanical design</subtitle>
<subtitle id='00:57:10'>particularly such as you do here at McDonnell Douglas require now for the</subtitle>
<subtitle id='00:57:17'>first time serious simulation of the</subtitle>
<subtitle id='00:57:21'>mechanical design particularly how it articulates with other parts of the</subtitle>
<subtitle id='00:57:25'>design really want to have a simulation job-shop built into the design system so</subtitle>
<subtitle id='00:57:32'>you can do a lot more than just finite element analysis but be able to do</subtitle>
<subtitle id='00:57:37'>analysis of linkages and other kinds of situations that are too difficult to do</subtitle>
<subtitle id='00:57:44'>simple in analytic solutions or do finite element analysis and the answer</subtitle>
<subtitle id='00:57:49'>to this is a kind of constraint driven object-oriented design the sketchpad</subtitle>
<subtitle id='00:57:55'>actually invented the first kind of so let me give you another example I'm</subtitle>
<subtitle id='00:57:59'>going to go to the number four tape this</subtitle>
<subtitle id='00:58:04'>time though</subtitle>
<subtitle id='00:58:13'>okay okay I'll pause well had some</subtitle>
<subtitle id='00:58:29'>interesting questions actually one of</subtitle>
<subtitle id='00:58:36'>the things I should have mentioned at the beginning is I'm perfectly happy to entertain questions that at any point I</subtitle>
<subtitle id='00:58:42'>believe that the the we have an hour and</subtitle>
<subtitle id='00:58:47'>a half that the at least an hour of the</subtitle>
<subtitle id='00:58:54'>hour and a half I think we should spend talking about issues that concern all of</subtitle>
<subtitle id='00:59:01'>us about object-oriented programming I have some of my own people who are</subtitle>
<subtitle id='00:59:06'>starting out on it may have some crap you the trepidation they may wonder</subtitle>
<subtitle id='00:59:11'>where it's going what the actual leverage is I had a a question asked</subtitle>
<subtitle id='00:59:19'>again about the difference between abstract data structures and what I</subtitle>
<subtitle id='00:59:24'>think of as a real object-oriented style another question was asked about is</subtitle>
<subtitle id='00:59:29'>there any way of preserving already written COBOL and Fortran code in an</subtitle>
<subtitle id='00:59:34'>object-oriented fashion so it doesn't</subtitle>
<subtitle id='00:59:38'>all have to be thrown away and maybe</subtitle>
<subtitle id='00:59:43'>that last question is one that's worth while answering now a lot of companies</subtitle>
<subtitle id='00:59:50'>are trying to figure out what to do</subtitle>
<subtitle id='00:59:55'>about object-oriented programming particularly given that there don't</subtitle>
<subtitle id='01:00:01'>exist any good object-oriented programming languages for programming in</subtitle>
<subtitle id='01:00:05'>the large small talk is not a good</subtitle>
<subtitle id='01:00:09'>language for programming in the large as it's currently distributed it's a great</subtitle>
<subtitle id='01:00:14'>language for learning about object-oriented programming because it's</subtitle>
<subtitle id='01:00:19'>written entirely in itself and so you can learn how an operating system how a</subtitle>
<subtitle id='01:00:25'>user interface how applications how little things and</subtitle>
<subtitle id='01:00:31'>larger things can be represented in an object-oriented form how inheritance</subtitle>
<subtitle id='01:00:37'>subclassing and so forth all those things small talk is ideal the of the</subtitle>
<subtitle id='01:00:43'>small talks around to look at the one</subtitle>
<subtitle id='01:00:47'>that has the best manual is the one called small talk V and it runs on both</subtitle>
<subtitle id='01:00:53'>the IBM PC and the Macintosh it's not</subtitle>
<subtitle id='01:00:59'>the mote it's it's a rather complete system in in a number of ways the other</subtitle>
<subtitle id='01:01:08'>system is called Park Place small talk small talk</subtitle>
<subtitle id='01:01:12'>8e and it is sort of the granddaddy of the small talks that that Xerox has</subtitle>
<subtitle id='01:01:20'>released it has a even more complete set</subtitle>
<subtitle id='01:01:25'>of system tools and some very ambitious</subtitle>
<subtitle id='01:01:29'>applications written in it both of those are worthwhile looking at</subtitle>
<subtitle id='01:01:35'>but for programming in the large objects</subtitle>
<subtitle id='01:01:40'>aren't enough I don't believe and the reason is that at some point it's not</subtitle>
<subtitle id='01:01:47'>simply a matter of piecing together something that is supposed to run it's a</subtitle>
<subtitle id='01:01:53'>matter of being able to verify different</subtitle>
<subtitle id='01:02:00'>sections different parts different modules independently to be able to</subtitle>
<subtitle id='01:02:04'>unplug and replug and even I think in</subtitle>
<subtitle id='01:02:08'>many cases it's desirable to allow different implementation languages to</subtitle>
<subtitle id='01:02:14'>actually be used now if we look at the</subtitle>
<subtitle id='01:02:20'>the standard</subtitle>
<subtitle id='01:02:33'>so we have a glob and the main principle in object-oriented programming is to</subtitle>
<subtitle id='01:02:38'>separate the outside from the inside so</subtitle>
<subtitle id='01:02:43'>on the outside we have a variety of</subtitle>
<subtitle id='01:02:48'>messages that we're willing to respond to and on the inside we have some</subtitle>
<subtitle id='01:02:54'>methods oh sorry</subtitle>
<subtitle id='01:03:01'>we have some methods the may or may not</subtitle>
<subtitle id='01:03:06'>correspond to these things on the outside cuz whatever the idea is we're</subtitle>
<subtitle id='01:03:10'>not supposed to understand what the inside looks at from looking at me on</subtitle>
<subtitle id='01:03:15'>the outside and outside thing might even correspond to a little data structure</subtitle>
<subtitle id='01:03:21'>inside a thing equally innocent might</subtitle>
<subtitle id='01:03:25'>correspond to an enormous amount of code there might be code in here not directly</subtitle>
<subtitle id='01:03:30'>connected to this and in fact some of the messages that the object may be able</subtitle>
<subtitle id='01:03:35'>to receive aren't directly characterized in terms of some outside protocol lots</subtitle>
<subtitle id='01:03:43'>of different variations here but the most important one here is that we're</subtitle>
<subtitle id='01:03:48'>trying to separate a protocol</subtitle>
<subtitle id='01:03:58'>from some methods</subtitle>
<subtitle id='01:04:07'>at this level and then if we think about going a little bit more fine-grain where</subtitle>
<subtitle id='01:04:12'>we started having zillions of objects interacting</subtitle>
<subtitle id='01:04:24'>in a sea of messages</subtitle>
<subtitle id='01:04:29'>in fact some of the</subtitle>
<subtitle id='01:04:36'>some of the objects might not even be on the same machine they might actually be</subtitle>
<subtitle id='01:04:40'>over here a good object-oriented system</subtitle>
<subtitle id='01:04:46'>you shouldn't be able to tell what machine you're running on that's what</subtitle>
<subtitle id='01:04:50'>messages are all about very quickly when</subtitle>
<subtitle id='01:04:54'>we're starting to build a large system down here we've got something</subtitle>
<subtitle id='01:04:58'>interesting we have absolute protection but we still have confusion right</subtitle>
<subtitle id='01:05:03'>because it's you can have thousands of</subtitle>
<subtitle id='01:05:08'>thousands of diamonds that are impervious to all normal wear and tear</subtitle>
<subtitle id='01:05:15'>and still not be able to build the simplest structure out of them they may</subtitle>
<subtitle id='01:05:19'>need to be too shiny may not be able to pile them up they may not fit together</subtitle>
<subtitle id='01:05:23'>but by god they're perfect so what I'm</subtitle>
<subtitle id='01:05:27'>trying to say is that the the protection issue is a critical one but it still</subtitle>
<subtitle id='01:05:32'>doesn't guarantee that you actually have an architecture now in small talk in the</subtitle>
<subtitle id='01:05:40'>most object-oriented systems how you come up with these guys is govern very</subtitle>
<subtitle id='01:05:46'>much by convention there's a particular</subtitle>
<subtitle id='01:05:50'>way like it's a convention in small talk systems that one of these guys will always be called print so that for every</subtitle>
<subtitle id='01:05:58'>object in the system you're guaranteed that one of the messages you can send to</subtitle>
<subtitle id='01:06:02'>it is print and theoretically what that</subtitle>
<subtitle id='01:06:08'>means is this little patch of green in</subtitle>
<subtitle id='01:06:12'>here that corresponds to print is</subtitle>
<subtitle id='01:06:16'>supposed to print for you now there's nothing in small talk or any other</subtitle>
<subtitle id='01:06:21'>object oriented system right now that guarantees that printing is going to be</subtitle>
<subtitle id='01:06:28'>done now there was a strictly conventional it's something that</subtitle>
<subtitle id='01:06:33'>everybody agrees to it's like overloading operators in Ada when you</subtitle>
<subtitle id='01:06:39'>overload plus in order to give plus more</subtitle>
<subtitle id='01:06:43'>meanings for different structures you're usually trying to adhere to something</subtitle>
<subtitle id='01:06:50'>metaphorically similar to what plus originally stood for so for instance if</subtitle>
<subtitle id='01:06:55'>you have a plus a plus it adds two numbers together you might overload it</subtitle>
<subtitle id='01:07:00'>to apply two arrays so that the operation is some sort of point point</subtitle>
<subtitle id='01:07:07'>point addition maybe vector addition sometimes you might overload strings -</subtitle>
<subtitle id='01:07:15'>what could + mean and strings well one of the one of the ways of thinking about</subtitle>
<subtitle id='01:07:19'>strings algebraically is that plus means concatenation because it's a way of</subtitle>
<subtitle id='01:07:24'>adding two unary numbers together and so forth and at some point you started</subtitle>
<subtitle id='01:07:29'>stretching it as you stretch the metaphor but generally you don't want</subtitle>
<subtitle id='01:07:33'>Plus to go off and do some sort of multiply or something else but the only</subtitle>
<subtitle id='01:07:38'>thing that controls that is some agreed on set of conventions and because of</subtitle>
<subtitle id='01:07:45'>that what this protocol is how complicated it gets and so forth is the</subtitle>
<subtitle id='01:07:51'>most important part in any kind of object-oriented design but it's also the</subtitle>
<subtitle id='01:07:55'>most fragile the fact that there's</subtitle>
<subtitle id='01:07:59'>nothing to protect print is absolutely</subtitle>
<subtitle id='01:08:04'>critical let me let me give you an example of what we could do to protect</subtitle>
<subtitle id='01:08:08'>print</subtitle>
<subtitle id='01:08:17'>one of the things we could do is to have</subtitle>
<subtitle id='01:08:22'>instead of having print just be code we</subtitle>
<subtitle id='01:08:26'>could actually have a print class</subtitle>
<subtitle id='01:08:38'>and its offspring its instances are</subtitle>
<subtitle id='01:08:42'>actually structures that look like this</subtitle>
<subtitle id='01:09:15'>okay in other words each offspring of print is a message method pair in which</subtitle>
<subtitle id='01:09:28'>unrestricted code writing over here is not allowed does everybody understand</subtitle>
<subtitle id='01:09:34'>why this is an interesting idea because</subtitle>
<subtitle id='01:09:39'>so but if you could only if you can write anything here then J random</subtitle>
<subtitle id='01:09:44'>programmer often will as you go as you</subtitle>
<subtitle id='01:09:49'>go along and the fact that the system seems to be conventionalized at this</subtitle>
<subtitle id='01:09:53'>protocol message level which is the very</subtitle>
<subtitle id='01:09:57'>charm of object-oriented programming why object-oriented programs work so well why they fit together gets destroyed as</subtitle>
<subtitle id='01:10:04'>the amount of generic information in the</subtitle>
<subtitle id='01:10:09'>actual methods gets diluted but if</subtitle>
<subtitle id='01:10:13'>another way of doing an object-oriented system is to actually make classes for</subtitle>
<subtitle id='01:10:20'>each of the major code types that you're going to write and what you get here is</subtitle>
<subtitle id='01:10:24'>something that would insert itself in here but in fact the only codes you're</subtitle>
<subtitle id='01:10:33'>allowed to write are certain little restricted boxes in here and this thing</subtitle>
<subtitle id='01:10:37'>guarantees that it's going to print for you it's not going to go off in zero</subtitle>
<subtitle id='01:10:41'>byte five of some system file this thing</subtitle>
<subtitle id='01:10:45'>because it came from a print class and because the print class does printing</subtitle>
<subtitle id='01:10:49'>type things every piece of code that goes into a protocol actually is going</subtitle>
<subtitle id='01:10:54'>to do something like printing and what you're allowed now is a certain amount</subtitle>
<subtitle id='01:10:58'>of parameterization a certain amount of freedom but the meaning of print now has</subtitle>
<subtitle id='01:11:04'>been nailed down because there's some actual code from the print class</subtitle>
<subtitle id='01:11:09'>sticking behind here that you can't see that's going to make every effort to</subtitle>
<subtitle id='01:11:14'>deliver a result that is what you want this is like types in type languages</subtitle>
<subtitle id='01:11:21'>except it's stronger because it can controls the goal of the result the goal</subtitle>
<subtitle id='01:11:27'>of the result not the shape of the result right in a typed</subtitle>
<subtitle id='01:11:33'>language when you have a typed variable or type procedure what you can state is</subtitle>
<subtitle id='01:11:39'>that might have some integer parameters and I'm going to deliver a</subtitle>
<subtitle id='01:11:43'>floating-point result what you can't say</subtitle>
<subtitle id='01:11:47'>in the type statement is what the intent of that procedure was the only intent</subtitle>
<subtitle id='01:11:52'>that you could indicate is that's going to in it's going to give you some sort of floating-point result you can't say</subtitle>
<subtitle id='01:11:58'>it was supposed to give you a sine or cosine or anything else that is up to</subtitle>
<subtitle id='01:12:04'>the convention of the actual programmer</subtitle>
<subtitle id='01:12:09'>itself so what I'm just pointing out here is that if you take a if you take a</subtitle>
<subtitle id='01:12:16'>system in which there is a protocol you</subtitle>
<subtitle id='01:12:20'>can get a lot out of it just by having the protocol be a convention agreed on</subtitle>
<subtitle id='01:12:25'>by everybody as you go into a larger and larger system that that inside out</subtitle>
<subtitle id='01:12:32'>outside Ness will protect against the inside getting dissolved by some hostile</subtitle>
<subtitle id='01:12:40'>act action by the outside but what will get diluted as you go to a larger and</subtitle>
<subtitle id='01:12:44'>larger system with more and more programmers is whether the protocol is</subtitle>
<subtitle id='01:12:49'>going to have any meaning practical example in small talk has approximately</subtitle>
<subtitle id='01:12:57'>Park Place small talk has approximately</subtitle>
<subtitle id='01:13:02'>5000 of these green things each one of</subtitle>
<subtitle id='01:13:06'>them is there each one of them can be reused by inheriting it from somebody</subtitle>
<subtitle id='01:13:11'>else the number of red things it has is</subtitle>
<subtitle id='01:13:15'>on the order of twenty one hundred that</subtitle>
<subtitle id='01:13:20'>means that the amount of how generic the</subtitle>
<subtitle id='01:13:25'>code is with respect to the protocol is not much right it should the number</subtitle>
<subtitle id='01:13:31'>should be more like 400 or so different red things four hundred concepts and say</subtitle>
<subtitle id='01:13:38'>five thousand realizations of those concepts now print is the happy exam exception to</subtitle>
<subtitle id='01:13:44'>that because if you have a 154 different kinds of objects than their 154</subtitle>
<subtitle id='01:13:51'>different green guys and only but only one print concept so there's the same</subtitle>
<subtitle id='01:13:58'>technique that people use overloading of operators for you want to reduce the concept space by making it more</subtitle>
<subtitle id='01:14:03'>algebraic make take a concept make as</subtitle>
<subtitle id='01:14:07'>metaphorical as you possibly can and</subtitle>
<subtitle id='01:14:11'>like equal is a good one what does equal mean some systems that</subtitle>
<subtitle id='01:14:17'>means we have I'm looking at exactly the same thing some systems it's okay for</subtitle>
<subtitle id='01:14:23'>the same if the same things look the same some systems is if under some</subtitle>
<subtitle id='01:14:28'>particular evaluation rule they evaluate to the same thing or they might evaluate</subtitle>
<subtitle id='01:14:32'>to the same thing so equal is one of these very slippery notions because it</subtitle>
<subtitle id='01:14:37'>very quickly becomes useful to think of equal as being very useful in terms of</subtitle>
<subtitle id='01:14:44'>equivalent this is equivalent to that</subtitle>
<subtitle id='01:14:48'>that's a generic notion so again you might imagine that one of the one of the</subtitle>
<subtitle id='01:14:54'>things you might like to have be generic</subtitle>
<subtitle id='01:15:00'>are comparisons equal equal is a much</subtitle>
<subtitle id='01:15:04'>stronger one of course than greater than or less than because greater than less than involve some sort of sorting but</subtitle>
<subtitle id='01:15:10'>again greater than and less than don't have to apply just two numbers in small</subtitle>
<subtitle id='01:15:15'>talk there's a super class called magnitudes and anything that can be</subtitle>
<subtitle id='01:15:21'>sorted in any way under any kind of sorting rule is underneath magnitudes</subtitle>
<subtitle id='01:15:26'>and underneath magnitudes are things</subtitle>
<subtitle id='01:15:30'>like less than and greater than</subtitle>
<subtitle id='01:15:35'>so for instance dates are an example</subtitle>
<subtitle id='01:15:39'>times time intervals anything that can be sorted in any in any form you can</subtitle>
<subtitle id='01:15:46'>those what you might what you would call operators in a de or automatically</subtitle>
<subtitle id='01:15:51'>overloaded now what happens in an</subtitle>
<subtitle id='01:15:56'>object-oriented start off with a nice set of these and then as practical</subtitle>
<subtitle id='01:16:02'>programmers chew on it the heat of debugging one of the things we</subtitle>
<subtitle id='01:16:06'>discovered is that even good programmers don't make up generic operators for</subtitle>
<subtitle id='01:16:14'>things what they do is they make up any old word think they can think of at the moment write a method for it and</subtitle>
<subtitle id='01:16:19'>continue on the result is that what the</subtitle>
<subtitle id='01:16:24'>object-oriented style was buying for you starts diluting it starts gradually</subtitle>
<subtitle id='01:16:29'>diluting away the manuals get larger and</subtitle>
<subtitle id='01:16:34'>all of a sudden you're back to something that is close to what you had before so</subtitle>
<subtitle id='01:16:39'>I'm not I'm not sure if people didn't understand this explanation I'll be glad</subtitle>
<subtitle id='01:16:46'>to go over it again because it's it's</subtitle>
<subtitle id='01:16:50'>it's one of the important examples of something that you can actually do with an object-oriented system everybody more</subtitle>
<subtitle id='01:16:56'>let's get what I was talking about that you can actually legislate one of the</subtitle>
<subtitle id='01:17:00'>things you can do in an object-oriented system is to legislate to some extent</subtitle>
<subtitle id='01:17:04'>even what the code that the programmer is going to write is going to deliver to</subtitle>
<subtitle id='01:17:08'>you you can build in to these main</subtitle>
<subtitle id='01:17:13'>concept classes the tests to see whether</subtitle>
<subtitle id='01:17:17'>the code is it all behaving the way you think it is those tests can be run</subtitle>
<subtitle id='01:17:22'>independently of the programmers who are writing the code now another thing you</subtitle>
<subtitle id='01:17:27'>can do using these protocol ideas is</subtitle>
<subtitle id='01:17:31'>horrible as it sounds there's no reason why you can't put some COBOL in here</subtitle>
<subtitle id='01:17:38'>this is not something that people do in</subtitle>
<subtitle id='01:17:42'>a typical object-oriented language like small talk because it's designed to to</subtitle>
<subtitle id='01:17:48'>write all of the methods in itself but if you think about this whole notion</subtitle>
<subtitle id='01:17:55'>here as a binding mechanism for a component not just as a way of</subtitle>
<subtitle id='01:18:01'>protecting a data structure but a binding mechanism as a component then</subtitle>
<subtitle id='01:18:05'>what you really are programming in terms with is the blue and the red what the</subtitle>
<subtitle id='01:18:16'>green is is almost completely independent as long as it conforms to</subtitle>
<subtitle id='01:18:24'>whatever this guy wants it to be able to do what I advise large companies when</subtitle>
<subtitle id='01:18:31'>they are embarking on object-oriented programming is to do a few systems using</subtitle>
<subtitle id='01:18:36'>something like small talk or preferably just to get an idea of what it's about</subtitle>
<subtitle id='01:18:42'>but then think of all the things that you've already learned about controlling</subtitle>
<subtitle id='01:18:46'>modules and systems and realize that the</subtitle>
<subtitle id='01:18:50'>small sizes of the code of the small talks from the 70s don't have all the</subtitle>
<subtitle id='01:18:54'>protections in there that you actually need what you really need is what these</subtitle>
<subtitle id='01:18:58'>days is called a configuration language a C language configuration language</subtitle>
<subtitle id='01:19:13'>and this language can be independent of all of your method languages it's it's</subtitle>
<subtitle id='01:19:19'>something that is dealt with it the operating system-level it's something in</subtitle>
<subtitle id='01:19:23'>which the protocols are chosen as much as possible ahead of time it's a</subtitle>
<subtitle id='01:19:28'>standard vocabulary of concepts that you're going to use to write in it's one</subtitle>
<subtitle id='01:19:32'>in which the protocols are controlled by active code the give you places to write</subtitle>
<subtitle id='01:19:38'>code and insert other code that allow you to bring over a COBOL routine or a</subtitle>
<subtitle id='01:19:43'>Fortran routine or whatever the heck you want and bind it in it's a binding</subtitle>
<subtitle id='01:19:47'>mechanism it's a way of setting up</subtitle>
<subtitle id='01:19:51'>environments for debugging modules</subtitle>
<subtitle id='01:19:56'>independently of each other it's a way of assuring yourself that a module will</subtitle>
<subtitle id='01:20:00'>be able to move from one place to another it's a way of discovering</subtitle>
<subtitle id='01:20:04'>whether you want to use a module so at</subtitle>
<subtitle id='01:20:08'>some point the ability for human to read this configuration language is going to</subtitle>
<subtitle id='01:20:12'>be much more important than the ability to write it one of the embarrassments</subtitle>
<subtitle id='01:20:18'>that you often find in an object-oriented language is you have all</subtitle>
<subtitle id='01:20:22'>of us we have usable code and it's too hard to find the modules you want to</subtitle>
<subtitle id='01:20:27'>reuse small talk has a lot of that flavor anybody who's ever tried</subtitle>
<subtitle id='01:20:32'>programming and especially in small talk 80 is bewildered by the fact that the</subtitle>
<subtitle id='01:20:39'>system is completely written in itself there are tons of usable things in there</subtitle>
<subtitle id='01:20:43'>and yet it is such a pain to find those things you wind up tandem out having to</subtitle>
<subtitle id='01:20:48'>read other people's code and then in order to find out whether you actually</subtitle>
<subtitle id='01:20:54'>want to use the stuff so the for instance what Arthur Andersen is doing</subtitle>
<subtitle id='01:20:59'>right now is to try and come up with</subtitle>
<subtitle id='01:21:04'>something that is completely independent just completely x-out forget about the</subtitle>
<subtitle id='01:21:12'>interior stuff just come up with something that is basically modules in</subtitle>
<subtitle id='01:21:17'>terms of blues and Red's making the the</subtitle>
<subtitle id='01:21:21'>red message protocol be as powerful as possible controlled by other things and</subtitle>
<subtitle id='01:21:25'>then using that as a dynamic binding mechanism for</subtitle>
<subtitle id='01:21:30'>configuring programs it allows them to</subtitle>
<subtitle id='01:21:34'>take large sections of database and</subtitle>
<subtitle id='01:21:38'>sequel calls that they've already done and bind it into an object-oriented</subtitle>
<subtitle id='01:21:42'>framework as an example yeah yeah</subtitle>
<subtitle id='01:21:57'>so configuration</subtitle>
<subtitle id='01:22:02'>let's start off with the things that you might want to have in it now the there's</subtitle>
<subtitle id='01:22:08'>only I only know of one actually good configuration language that's been done</subtitle>
<subtitle id='01:22:13'>as a language called C Mesa which was</subtitle>
<subtitle id='01:22:17'>done by the Parc computer science lab</subtitle>
<subtitle id='01:22:21'>about ten years ago and it served</subtitle>
<subtitle id='01:22:25'>exactly this this purpose and here are some of the things can have it there are</subtitle>
<subtitle id='01:22:31'>some things that you'd expect just from your previous experience you'd expect</subtitle>
<subtitle id='01:22:36'>that there would be some sort of message name for something you'd expect that</subtitle>
<subtitle id='01:22:45'>there would be I Oh parameters so that</subtitle>
<subtitle id='01:22:53'>you would have input expectations</subtitle>
<subtitle id='01:23:02'>output expectation</subtitle>
<subtitle id='01:23:11'>a good configuration language has a an executable predicate you can think of as</subtitle>
<subtitle id='01:23:19'>a goal that they may have a variety of</subtitle>
<subtitle id='01:23:26'>them and I connect those with when I say</subtitle>
<subtitle id='01:23:31'>input expectations I mean not just the</subtitle>
<subtitle id='01:23:35'>types of the parameters that you expect to send to it and the types of the</subtitle>
<subtitle id='01:23:40'>results but also these predicates sorry</subtitle>
<subtitle id='01:23:47'>predicates you can think of</subtitle>
<subtitle id='01:23:52'>preconditions on the input side and goals on the output side</subtitle>
<subtitle id='01:24:04'>you can think of those as being executable there are environmental</subtitle>
<subtitle id='01:24:17'>expectations</subtitle>
<subtitle id='01:24:22'>one of the difficulties in most object-oriented programming languages is</subtitle>
<subtitle id='01:24:26'>although you can protect an object what</subtitle>
<subtitle id='01:24:30'>you don't have any sense of when you want to move an object is what the</subtitle>
<subtitle id='01:24:34'>object itself expects to have as environment as a give you an example in</subtitle>
<subtitle id='01:24:42'>small talk you can write an object move</subtitle>
<subtitle id='01:24:49'>it for one place of a particular Smalltalk system to another but when you</subtitle>
<subtitle id='01:24:54'>want to take it out of your small talk system and give it to somebody else a small talk system you often are</subtitle>
<subtitle id='01:24:58'>unpleasantly surprised and it's not that</subtitle>
<subtitle id='01:25:02'>the object has been solid in any way it's that it has some other assumptions</subtitle>
<subtitle id='01:25:07'>about its environment that you weren't thinking about before in particular</subtitle>
<subtitle id='01:25:13'>small talk allows you to do the somewhat obscene thing of allowing you to go and</subtitle>
<subtitle id='01:25:20'>change existing super classes to make them more the way you like the benefit</subtitle>
<subtitle id='01:25:26'>of this is that every class and the system feels this improvement and the</subtitle>
<subtitle id='01:25:30'>problem with it is if that improvement is important then you've all of a sudden</subtitle>
<subtitle id='01:25:34'>have done away with your portability so what I'm trying to point out here is</subtitle>
<subtitle id='01:25:39'>that the modularity you get in object-oriented programming is slippery</subtitle>
<subtitle id='01:25:43'>and one of the most critical things to do is to be able to pin down the amount</subtitle>
<subtitle id='01:25:50'>of modularity that's actually there I'm gonna I'm going to go into that in a</subtitle>
<subtitle id='01:25:54'>little more detail so the there are more</subtitle>
<subtitle id='01:26:00'>things that are here people have design</subtitle>
<subtitle id='01:26:06'>configurations languages in such a form that you can actually from the runnable</subtitle>
<subtitle id='01:26:13'>parts of the stuff that you can actually derive an explanation mechanically of what the method and what</subtitle>
<subtitle id='01:26:21'>the module itself is supposed to do</subtitle>
<subtitle id='01:26:30'>okay so there are any number of things</subtitle>
<subtitle id='01:26:34'>basically it's something a little bit more close closer in spirit to Parnas</subtitle>
<subtitle id='01:26:40'>they've partners who did one of the original notions about information</subtitle>
<subtitle id='01:26:44'>hiding although it wasn't object-oriented than what you might think of as straight object-oriented</subtitle>
<subtitle id='01:26:49'>doctrine and that each one of these these things is part of</subtitle>
<subtitle id='01:27:04'>this blue</subtitle>
<subtitle id='01:27:10'>no Sheena that this forms a class from</subtitle>
<subtitle id='01:27:17'>which we get the various instances that</subtitle>
<subtitle id='01:27:21'>our system is actually made up of so each each a little instance</subtitle>
<subtitle id='01:27:41'>now it is often the case that if these</subtitle>
<subtitle id='01:27:47'>two predicates here are done correctly you can actually run you do your</subtitle>
<subtitle id='01:27:53'>prototyping by running the blue thing essentially without any green things</subtitle>
<subtitle id='01:28:00'>inside of it or you can think of it</subtitle>
<subtitle id='01:28:04'>being just tiny little green things that come along because of what these are yes</subtitle>
<subtitle id='01:28:17'>okay the this is it's similar to ADA</subtitle>
<subtitle id='01:28:23'>except that ADA for instance doesn't have inheritance and so does everybody</subtitle>
<subtitle id='01:28:30'>here understand what I'm not sure I didn't come to give a tutorial so I'm</subtitle>
<subtitle id='01:28:34'>not sure what I'm what I was supposed to assume everybody knows about the thing but in most object-oriented languages is</subtitle>
<subtitle id='01:28:40'>this notion of inheritance that you can</subtitle>
<subtitle id='01:28:45'>define something very general and abstract like</subtitle>
<subtitle id='01:28:55'>say a thing called a magnitude</subtitle>
<subtitle id='01:29:02'>in a magnitude maybe something even more</subtitle>
<subtitle id='01:29:07'>abs I mean let me use the fresh sheet of paper</subtitle>
<subtitle id='01:29:14'>start off with something really abstract like a general object and then one of</subtitle>
<subtitle id='01:29:25'>the operations and an object you might want to have for every object is</subtitle>
<subtitle id='01:29:29'>equality then a little less abstract you</subtitle>
<subtitle id='01:29:36'>might have something called a magnitude</subtitle>
<subtitle id='01:29:40'>one of its operations might be less than</subtitle>
<subtitle id='01:29:46'>but there still that might not be any notion of what addition is coming down a</subtitle>
<subtitle id='01:29:52'>little bit further you might have something called a number and it might</subtitle>
<subtitle id='01:29:59'>have a notion of plus and there might be</subtitle>
<subtitle id='01:30:05'>a various specializations of numbers so you might have an integer a fraction</subtitle>
<subtitle id='01:30:15'>these guys might have their own versions of plus the notion of inheritance is</subtitle>
<subtitle id='01:30:21'>that very often you can get a compact</subtitle>
<subtitle id='01:30:26'>sorry you can get a compact description</subtitle>
<subtitle id='01:30:30'>of a wide variety of behaviors by</subtitle>
<subtitle id='01:30:35'>factoring out behavior as abstract li as</subtitle>
<subtitle id='01:30:39'>you possibly can you move it as high as you possibly can and occasionally you</subtitle>
<subtitle id='01:30:44'>may have to give your own versions of things like integer may want its own</subtitle>
<subtitle id='01:30:50'>version of what plus generally is it may</subtitle>
<subtitle id='01:30:54'>even want to have its own version of what less than is or may be able to use this general one up here and but</subtitle>
<subtitle id='01:31:02'>inheritance actually allows you to</subtitle>
<subtitle id='01:31:06'>cascade descriptions and in a number of</subtitle>
<subtitle id='01:31:10'>object-oriented systems particularly the AI ones you can actually blend them</subtitle>
<subtitle id='01:31:14'>together in various ways so you can actually say this this thing is not just</subtitle>
<subtitle id='01:31:20'>a number it is also a geometric object and inherit a bunch of things from the</subtitle>
<subtitle id='01:31:25'>side as well so what go to when I talk about doing the</subtitle>
<subtitle id='01:31:31'>configuration stuff I mean to imply all</subtitle>
<subtitle id='01:31:38'>the things that you usually do in a typed language but also applied to a</subtitle>
<subtitle id='01:31:46'>system that has inheritance because it's inheritance in object or any languages</subtitle>
<subtitle id='01:31:50'>is how you share things the goal of</subtitle>
<subtitle id='01:31:55'>release it has been the goal for the last 20 years of people who do this and</subtitle>
<subtitle id='01:31:59'>write very small very reusable very</subtitle>
<subtitle id='01:32:03'>compact code the goal goal is to make</subtitle>
<subtitle id='01:32:07'>the things that are shared as abstract</subtitle>
<subtitle id='01:32:11'>and inheritable as they possibly can be</subtitle>
<subtitle id='01:32:15'>so you want the smallest number of</subtitle>
<subtitle id='01:32:19'>maximally independent concepts that you</subtitle>
<subtitle id='01:32:24'>can Tinkertoy together and have some confidence that the active Tinkertoy is</subtitle>
<subtitle id='01:32:30'>going to give you something that also still works the whole idea in</subtitle>
<subtitle id='01:32:35'>object-oriented style is to linearly combine things together not a native</subtitle>
<subtitle id='01:32:39'>package allows you to subsume some of</subtitle>
<subtitle id='01:32:45'>the details of a data structure it does</subtitle>
<subtitle id='01:32:49'>not allow you for instance to define</subtitle>
<subtitle id='01:32:53'>generic operations which are then</subtitle>
<subtitle id='01:32:57'>inherited by subclasses because it simply doesn't allow you to subclass and</subtitle>
<subtitle id='01:33:03'>what that we leaves you add is a single single layer of description for</subtitle>
<subtitle id='01:33:08'>something which you can get instances from but you can't you generally Eneida</subtitle>
<subtitle id='01:33:12'>do not write an abstract thing that you're going to get in instances from</subtitle>
<subtitle id='01:33:17'>because usually these very abstract types like magnitude and so forth aren't</subtitle>
<subtitle id='01:33:23'>things that you want to use directly they're really placeholders for general</subtitle>
<subtitle id='01:33:27'>code and strategies and this is a foreign idea in the in the aid of</subtitle>
<subtitle id='01:33:32'>programming world which is almost entirely concrete yes</subtitle>
<subtitle id='01:33:37'>well I do to an actually ADA shouldn't</subtitle>
<subtitle id='01:33:42'>even really call them generics from but it's yeah it's okay anybody can use a</subtitle>
<subtitle id='01:33:47'>name for whatever they want but it's that's a it's a different way of</subtitle>
<subtitle id='01:33:51'>thinking about what generic is than what I'm thinking about here the generic power in an object-oriented programming</subtitle>
<subtitle id='01:33:56'>language is your ability to not just</subtitle>
<subtitle id='01:34:00'>reuse a concept sideways but also to advance it abstractly the more you can</subtitle>
<subtitle id='01:34:06'>advance it abstractly the more chance it has of being involved in in an abstract</subtitle>
<subtitle id='01:34:12'>design the less probability you have of having to recode whole strategy here's</subtitle>
<subtitle id='01:34:19'>is true is to avoid recoding remember we</subtitle>
<subtitle id='01:34:23'>got off on this thing I'm just pointing out there's just really just an aside</subtitle>
<subtitle id='01:34:27'>remark that you could make a very strong</subtitle>
<subtitle id='01:34:36'>object-oriented programming language by being completely independent of whatever</subtitle>
<subtitle id='01:34:43'>the methods are actually coded yet that was the whole point behind that</subtitle>
<subtitle id='01:34:48'>digression that as you build yourself object-oriented tools you're much better</subtitle>
<subtitle id='01:34:53'>off worrying about the integrity of the</subtitle>
<subtitle id='01:34:57'>individual objects and then the next thing is can an object be a component</subtitle>
<subtitle id='01:35:01'>and fit into some larger scale protocol</subtitle>
<subtitle id='01:35:05'>when I say a component I mean something like let's say a paragraph of text or</subtitle>
<subtitle id='01:35:11'>generic gear something that actually has a fair amount of meaning behind it might</subtitle>
<subtitle id='01:35:15'>even have its own inference engine as part of it talking about something that</subtitle>
<subtitle id='01:35:20'>can be used in a wide variety of cases in which the sharing is more than</subtitle>
<subtitle id='01:35:24'>parametric you're really getting not</subtitle>
<subtitle id='01:35:28'>just a class of things you're you're sharing a notion that somebody has come</subtitle>
<subtitle id='01:35:34'>up a concept a set of concepts that somebody has come up with this obscure</subtitle>
<subtitle id='01:35:43'>it's the hardest it's actually the</subtitle>
<subtitle id='01:35:47'>hardest thing to explain simply because I'm gonna try another pass at it one of</subtitle>
<subtitle id='01:35:55'>the reasons it's hard to explain is that the this notion because of ADA being</subtitle>
<subtitle id='01:36:01'>called object oriented being taught in school as being object oriented actually</subtitle>
<subtitle id='01:36:05'>has clouded the the issue considerably so it's very difficult to even explain</subtitle>
<subtitle id='01:36:12'>why some of these ideas are more complex let me give you another completely</subtitle>
<subtitle id='01:36:18'>different idea this has to do with</subtitle>
<subtitle id='01:36:23'>another way of thinking about modularity now in most object-oriented systems the</subtitle>
<subtitle id='01:36:35'>modularity that is gotten by them is one</subtitle>
<subtitle id='01:36:40'>that is regard to the state that you put</subtitle>
<subtitle id='01:36:44'>in each each object what isn't modular is the control</subtitle>
<subtitle id='01:36:52'>this is another set of issues to talk about so for example one of the things</subtitle>
<subtitle id='01:37:01'>that you may see when you're looking into an object-oriented programming is is you may see the state and each neatly</subtitle>
<subtitle id='01:37:06'>encapsulated but you may see control going all over the place what happens</subtitle>
<subtitle id='01:37:10'>when you send a message the answer is often I don't know goes here goes there and find somebody</subtitle>
<subtitle id='01:37:16'>here talks to this guy dozens of things happen and I can't even tell whether</subtitle>
<subtitle id='01:37:22'>control is ever going to get back to me that's often the state of affairs now</subtitle>
<subtitle id='01:37:29'>what would happen if we actually made control modular</subtitle>
<subtitle id='01:37:41'>we'd have something more like this where</subtitle>
<subtitle id='01:37:46'>instead of control going through the objects the objects themselves are</subtitle>
<subtitle id='01:37:50'>sitting in a sea of messages but they</subtitle>
<subtitle id='01:37:54'>don't actually originate them themselves how is that possible well one way you</subtitle>
<subtitle id='01:38:01'>can imagine for it to be possible is for the objects to simply say I need to know</subtitle>
<subtitle id='01:38:10'>the following put needs in here</subtitle>
<subtitle id='01:38:31'>now the object there are object-oriented system is one of the ones we've just</subtitle>
<subtitle id='01:38:35'>developed at Apple one that we did at MIT is an object-oriented system in</subtitle>
<subtitle id='01:38:40'>which you never send a message okay you</subtitle>
<subtitle id='01:38:45'>only receive how is it possible well the</subtitle>
<subtitle id='01:38:49'>system contrives to make the messages get to you by looking at your needs and</subtitle>
<subtitle id='01:38:55'>looking around to see who might supply those needs</subtitle>
<subtitle id='01:38:59'>okay is this obscure okay so an example</subtitle>
<subtitle id='01:39:06'>is suppose your</subtitle>
<subtitle id='01:39:17'>suppose you're a a button whose job it</subtitle>
<subtitle id='01:39:24'>is to move the corner of a window so one</subtitle>
<subtitle id='01:39:29'>of the ways of programming that is for</subtitle>
<subtitle id='01:39:33'>you to be in a loop constantly looking</subtitle>
<subtitle id='01:39:37'>to see if the mouse is coming into you okay it's a polling solution to the</subtitle>
<subtitle id='01:39:43'>problem where somebody is polling somewhere but you're constantly looking</subtitle>
<subtitle id='01:39:47'>to see whether the mouse is coming in when the mouse comes in then you say okay now I know what to do I'm going to</subtitle>
<subtitle id='01:39:54'>latch on to the mouse's coordinates and I'm going to tell my window owner</subtitle>
<subtitle id='01:40:00'>exactly how he should be moved around and so as we move around the corner the</subtitle>
<subtitle id='01:40:04'>window corner moves around itself and so</subtitle>
<subtitle id='01:40:10'>that's that's this kind of style of programming control is explicit we have</subtitle>
<subtitle id='01:40:15'>to poll to find out things that are going on the other way of doing it is I</subtitle>
<subtitle id='01:40:20'>could just say I need to know when the mouse comes in to me and then I can do</subtitle>
<subtitle id='01:40:29'>my job this is like an on condition but</subtitle>
<subtitle id='01:40:34'>it's an on condition that has to be scoped because we can't have it</subtitle>
<subtitle id='01:40:40'>happening every time the princess the mouse button goes down but we can</subtitle>
<subtitle id='01:40:45'>imagine that this guy can say okay I have a set of conditions I'm not going</subtitle>
<subtitle id='01:40:50'>to explicitly look for it I'm just going to tell the world that if I had these</subtitle>
<subtitle id='01:40:55'>conditions come true for me then I would be able to fulfill my</subtitle>
<subtitle id='01:41:03'>obligations to the rest of the system I'd know what to do likewise the window</subtitle>
<subtitle id='01:41:08'>that encloses this guy could also have a</subtitle>
<subtitle id='01:41:12'>set of conditions that say well if the corner if my corner guy starts moving I</subtitle>
<subtitle id='01:41:17'>should probably move too I'll change my size if he moves so if</subtitle>
<subtitle id='01:41:23'>only if somebody would let me know that then I'll go along see what this is like</subtitle>
<subtitle id='01:41:27'>this is like constraint programming okay we're going from</subtitle>
<subtitle id='01:41:31'>a procedural style which controls past</subtitle>
<subtitle id='01:41:35'>explicitly around to a declarative style in which were simply indicating needs</subtitle>
<subtitle id='01:41:40'>and the system without having to do any problem-solving is picking up the slack</subtitle>
<subtitle id='01:41:46'>by providing the actual information in the forms of messages HyperCard has this</subtitle>
<subtitle id='01:41:51'>about half way it's a technique we've been experimenting with at Apple for the</subtitle>
<subtitle id='01:41:56'>last couple of years and what it looks</subtitle>
<subtitle id='01:42:00'>like it's able to do is to completely</subtitle>
<subtitle id='01:42:04'>remove the necessity for actually being able to follow a control flow what does</subtitle>
<subtitle id='01:42:09'>this mean when you move an object from one place to another</subtitle>
<subtitle id='01:42:19'>when you move an object from some place into this kind of situation nothing is</subtitle>
<subtitle id='01:42:26'>going to happen with sorry kind of a</subtitle>
<subtitle id='01:42:30'>tiny screen isn't it and you put in when you move a new object in here in this</subtitle>
<subtitle id='01:42:36'>kind of situation nothing is going to happen to that object unless you go in</subtitle>
<subtitle id='01:42:40'>and recode somebody else in order to send it some messages right and so my</subtitle>
<subtitle id='01:42:47'>modularity of being able to move an object from one place to another depends</subtitle>
<subtitle id='01:42:52'>on me being able to do some kind of modification and the system is already</subtitle>
<subtitle id='01:42:56'>there that's not so good it's good in the sense that this object is guaranteed</subtitle>
<subtitle id='01:43:01'>not to hurt anybody and it's going to protect its own self from being moved</subtitle>
<subtitle id='01:43:06'>around but in fact I still have to go in and make some sort of modification in</subtitle>
<subtitle id='01:43:11'>order to get control the flow when I</subtitle>
<subtitle id='01:43:19'>put in a new blue guy here</subtitle>
<subtitle id='01:43:29'>and he has all his needs specified is he</subtitle>
<subtitle id='01:43:34'>going to be able to run why</subtitle>
<subtitle id='01:43:44'>because he doesn't have because the whole idea is that he's not intertwined</subtitle>
<subtitle id='01:43:51'>with anybody else's control he's simply saying I know what I need god damn it</subtitle>
<subtitle id='01:43:58'>then the question is can the system actually deliver those needs just</subtitle>
<subtitle id='01:44:02'>because he's a new thing and the answer seems to be yes this is a peek into the</subtitle>
<subtitle id='01:44:07'>object-oriented programming of the next couple of years in interesting you know</subtitle>
<subtitle id='01:44:12'>if this the need to do things this way came out of yet another project with</subtitle>
<subtitle id='01:44:16'>children all of the object-oriented stuff has developed at Park and the</subtitle>
<subtitle id='01:44:21'>Macintosh user interface came from a set</subtitle>
<subtitle id='01:44:25'>of designs to try and allow children to</subtitle>
<subtitle id='01:44:30'>do serious programming on a computer that was what forced object-oriented</subtitle>
<subtitle id='01:44:34'>programming out into the open the last set of stuff that we've been doing with</subtitle>
<subtitle id='01:44:38'>children at Apple forced this out of the open because we wanted children younger</subtitle>
<subtitle id='01:44:42'>than nine to be able to program and children younger than nine have a very</subtitle>
<subtitle id='01:44:46'>hard time following control flow of course when we're thinking about that</subtitle>
<subtitle id='01:44:51'>we're thinking well of course they have a hard time following control flow so do we except where you see the problem is</subtitle>
<subtitle id='01:44:59'>adults are used to suffering so it's why</subtitle>
<subtitle id='01:45:04'>I like why I like to design for children so designing this new programming</subtitle>
<subtitle id='01:45:08'>language for children I'm going to give you a little example of some of the stuff programmed in it this notion of</subtitle>
<subtitle id='01:45:17'>making control completely modular by going to a needs thing became apparent</subtitle>
<subtitle id='01:45:23'>yes</subtitle>
<subtitle id='01:45:27'>yes</subtitle>
<subtitle id='01:45:33'>yeah well it's complicated because I'll</subtitle>
<subtitle id='01:45:41'>give you I'll give you a simple example and then maybe we can generalize it a</subtitle>
<subtitle id='01:45:47'>little bit the motivation came from a couple of years ago of you know</subtitle>
<subtitle id='01:45:53'>wondering why it was so easy to program in spreadsheets and wondering what</subtitle>
<subtitle id='01:45:58'>spreadsheets would be like if there are more object oriented I've always thought of the spreadsheet cells as being almost</subtitle>
<subtitle id='01:46:03'>an object and spreadsheet cells have this nice characteristic that they they</subtitle>
<subtitle id='01:46:09'>are these aren't they in other words the</subtitle>
<subtitle id='01:46:13'>very act of writing the spreadsheet expression indicates to the rest of the</subtitle>
<subtitle id='01:46:17'>spreadsheet system what your needs are now usually they're pretty simple needs</subtitle>
<subtitle id='01:46:21'>they're just I need to know the values of so-and-so cells relative to where I I</subtitle>
<subtitle id='01:46:26'>am but I got interested in generalizing that and started off with a spreadsheet</subtitle>
<subtitle id='01:46:34'>system that I did in small talk that had</subtitle>
<subtitle id='01:46:38'>a spreadsheet optimizer that first started off simply trying to look at</subtitle>
<subtitle id='01:46:45'>places you wanted to get values from and building a propagation network rather</subtitle>
<subtitle id='01:46:49'>than executing every cell every for every change in this especially I think</subtitle>
<subtitle id='01:46:53'>most of you were aware that most spreadsheets today do not execute every</subtitle>
<subtitle id='01:46:57'>cell there's a propagation network built by the spreadsheet compiler that you</subtitle>
<subtitle id='01:47:01'>don't see that tries to find you the</subtitle>
<subtitle id='01:47:06'>minimal number of things that have to be executed every time the change is made</subtitle>
<subtitle id='01:47:11'>in the in the spreadsheet I started working on that and then the next thing</subtitle>
<subtitle id='01:47:16'>is to go to billions where you're interested in whenever something like</subtitle>
<subtitle id='01:47:21'>for instance whatever this is equal to that I would like to do something or</subtitle>
<subtitle id='01:47:27'>whenever this is less than that I'd like to do something and the I'll just give</subtitle>
<subtitle id='01:47:32'>you a hint of it</subtitle>
<subtitle id='01:47:44'>so they start out with this fairly</subtitle>
<subtitle id='01:47:50'>simple idea that if you have a variable somewhere one of the things that you can</subtitle>
<subtitle id='01:47:57'>do is to link you can have a link to all</subtitle>
<subtitle id='01:48:05'>of the different places that ever need</subtitle>
<subtitle id='01:48:10'>the value of that variable and when this</subtitle>
<subtitle id='01:48:15'>changes you simply fire off all of these guys and you get the desired result</subtitle>
<subtitle id='01:48:24'>let's take an expression now so we take</subtitle>
<subtitle id='01:48:30'>an expression like a is less than B or C</subtitle>
<subtitle id='01:48:39'>is greater than equal to D and then ask</subtitle>
<subtitle id='01:48:45'>what we'd have to do to that to make that efficient the answer is you make</subtitle>
<subtitle id='01:48:50'>this thing into a little tree and at each stage each node of the tree you</subtitle>
<subtitle id='01:48:59'>hold the very the value of the things so</subtitle>
<subtitle id='01:49:03'>far</subtitle>
<subtitle id='01:49:10'>so in this case the a value would be linked through here and you can think of</subtitle>
<subtitle id='01:49:17'>the tree is pointing upwards</subtitle>
<subtitle id='01:49:29'>okay and we can presume that this let's</subtitle>
<subtitle id='01:49:33'>make this an just for the heck of it</subtitle>
<subtitle id='01:49:42'>see that this is false and we assume that this is true and that this is false</subtitle>
<subtitle id='01:49:50'>let's do it the other way I make this true</subtitle>
<subtitle id='01:49:55'>this false so the idea is now if it</subtitle>
<subtitle id='01:50:00'>changes the insight here is that all you have to do is compare it to whatever the</subtitle>
<subtitle id='01:50:06'>current value of B is let's say this goes to to true you don't have to</subtitle>
<subtitle id='01:50:12'>recompute this guy because it didn't change it's already part of this frozen</subtitle>
<subtitle id='01:50:16'>result and then you come up and recompute this guy so you bait what you</subtitle>
<subtitle id='01:50:21'>basically have done in this technique is to have sorted the actual computation</subtitle>
<subtitle id='01:50:25'>that you have to make this this tech this way of doing things is called a</subtitle>
<subtitle id='01:50:30'>continuously evaluating expression</subtitle>
<subtitle id='01:50:41'>so it's a conglomerate of things it's actually a little computation engine designed to compute in parallel and only</subtitle>
<subtitle id='01:50:48'>the stuff that needs to get computed gets computed so you the computation now</subtitle>
<subtitle id='01:50:53'>the compiler instead of compiling machine code in a system like this is actually compiling a propagation people</subtitle>
<subtitle id='01:51:00'>are interested in these techniques I refer you to the books on functional programming mostly being written in</subtitle>
<subtitle id='01:51:07'>England these these days functional program is about this and well-behaved</subtitle>
<subtitle id='01:51:14'>functional programming languages have the property that you can take any computation that has variables in it and</subtitle>
<subtitle id='01:51:21'>through a fairly simple compilation change it into a network that has no</subtitle>
<subtitle id='01:51:27'>variables whatsoever but simply routing x' for values does that sound please</subtitle>
<subtitle id='01:51:33'>please interrupt me if that's it doesn't sound reasonable is that sound reason</subtitle>
<subtitle id='01:51:38'>it's intuitively reasonable isn't it because what does a variable as a place</subtitle>
<subtitle id='01:51:43'>you go to to get a value but of course you can what you really need in a</subtitle>
<subtitle id='01:51:48'>computation is simply a value delivered you don't need the value to be anywhere except where the operator is so by using</subtitle>
<subtitle id='01:51:56'>a combination of those techniques you can actually remarkably enough it's</subtitle>
<subtitle id='01:52:07'>actually it's always surprising when these things work you can actually go to</subtitle>
<subtitle id='01:52:12'>a thing that's an extreme generalization of a spreadsheet cell that does an</subtitle>
<subtitle id='01:52:19'>enormous amount of parallel computation but in a way in which you see none of</subtitle>
<subtitle id='01:52:24'>the interactions yourself</subtitle>
<subtitle id='01:52:31'>now because of production production system it it's not at odds with the</subtitle>
<subtitle id='01:52:37'>production system it's on this it's not like ops five as an example which is a</subtitle>
<subtitle id='01:52:43'>production system I understand people use here it's basically it's orthogonal</subtitle>
<subtitle id='01:52:50'>to whether there's a production system trying to do things or not</subtitle>
<subtitle id='01:52:54'>ops five has an example in which the you</subtitle>
<subtitle id='01:52:58'>have to order the rules yourself to a certain extent in order to in order to</subtitle>
<subtitle id='01:53:03'>get efficiency and so forth and you can</subtitle>
<subtitle id='01:53:08'>think of this as something which is independent of whether there are rules</subtitle>
<subtitle id='01:53:12'>and I didn't say there are rules here what I said is that what we actually are</subtitle>
<subtitle id='01:53:17'>interested in is whether there's whether there's a set of conditions that can</subtitle>
<subtitle id='01:53:21'>deliver to me what I actually need one of the things you could implement with</subtitle>
<subtitle id='01:53:26'>this idea is a production system I'm not</subtitle>
<subtitle id='01:53:30'>but it doesn't lie it isn't particularly like a production system you could</subtitle>
<subtitle id='01:53:34'>implement a production system using the idea though do you understand to say it just one it</subtitle>
<subtitle id='01:53:42'>yeah because it because some production systems have to be executed in sorry</subtitle>
<subtitle id='01:53:48'>we're getting killed for time we only have a half an hour so what I would like</subtitle>
<subtitle id='01:53:52'>to suggest is that we just sit still while they change the tape is that okay</subtitle>
<subtitle id='01:53:57'>should only take them 10 seconds</subtitle>
<subtitle id='01:54:11'>I was brought up about what do you do</subtitle>
<subtitle id='01:54:15'>with real time in fact what do you do with time and historically the first</subtitle>
<subtitle id='01:54:28'>object-oriented programs that were done outside of machine code were done in a</subtitle>
<subtitle id='01:54:33'>programming language called Simula and Simula had this way of looking at time</subtitle>
<subtitle id='01:54:38'>the Simula he had</subtitle>
<subtitle id='01:54:47'>a bunch of objects</subtitle>
<subtitle id='01:54:53'>one for each entity that you're trying</subtitle>
<subtitle id='01:54:57'>to model so the</subtitle>
<subtitle id='01:55:05'>these guys might be modeling pipes</subtitle>
<subtitle id='01:55:14'>and so forth and the blue the blue guys might be modeling reactors in a chemical</subtitle>
<subtitle id='01:55:23'>plant or something like that but</subtitle>
<subtitle id='01:55:27'>basically as far as seeing they're concerned they're all objects they're</subtitle>
<subtitle id='01:55:31'>all trying to execute at once trying to</subtitle>
<subtitle id='01:55:37'>get to the new trying to move advance the entire system time and they had this</subtitle>
<subtitle id='01:55:44'>problem of if you have a system time the system clock that's going on</subtitle>
<subtitle id='01:55:48'>how can you compute because you might</subtitle>
<subtitle id='01:55:52'>actually run out of time for computing</subtitle>
<subtitle id='01:55:57'>before you can actually advance to the next system time so what the similar people realize that they wanted to do</subtitle>
<subtitle id='01:56:03'>was in between the system clock so</subtitle>
<subtitle id='01:56:07'>system clock might be one and the next</subtitle>
<subtitle id='01:56:13'>time any of these guys had to compute</subtitle>
<subtitle id='01:56:17'>was two so what it would do is it would</subtitle>
<subtitle id='01:56:23'>do all of the computing in between the</subtitle>
<subtitle id='01:56:29'>ticks of the clock so the computing was actually outside the space of the simulation so Simula this is a non</subtitle>
<subtitle id='01:56:36'>real-time situation simular running on a mainframe would compute an arbitrary</subtitle>
<subtitle id='01:56:40'>amount in between each state change so</subtitle>
<subtitle id='01:56:44'>guarantee that each as much as it could possibly do it would settle down the</subtitle>
<subtitle id='01:56:48'>state of each one of these objects during this time when they were all in</subtitle>
<subtitle id='01:56:53'>process as soon as that that had happened then it would say okay now I</subtitle>
<subtitle id='01:56:57'>can go to the next time on the clock it is now - what do I have to do now then</subtitle>
<subtitle id='01:57:02'>the clock could be frozen would compute like mad again advance the clock again</subtitle>
<subtitle id='01:57:06'>now of course there's a huge conflict</subtitle>
<subtitle id='01:57:10'>that's the way you generally do it when you're doing object-oriented program</subtitle>
<subtitle id='01:57:14'>huge conflict between this and when you want to do real-time things because um</subtitle>
<subtitle id='01:57:19'>real-time things you don't get to stop the clock the clock is moving along</subtitle>
<subtitle id='01:57:25'>and of course one of the answers is if</subtitle>
<subtitle id='01:57:29'>you don't have enough computing power to compute before the next time the clock</subtitle>
<subtitle id='01:57:34'>ticks then you're dead anyway okay so let's assume that we have enough</subtitle>
<subtitle id='01:57:38'>computing power and just to ask what we</subtitle>
<subtitle id='01:57:42'>can do an object an object-oriented design to reconcile what time actually</subtitle>
<subtitle id='01:57:49'>means and the way people generally think</subtitle>
<subtitle id='01:57:54'>about time and object-oriented programming as time has entirely to do with who can view what when so it's a</subtitle>
<subtitle id='01:58:02'>viewing operation so let's suppose we have our objects here and we have some</subtitle>
<subtitle id='01:58:10'>views</subtitle>
<subtitle id='01:58:18'>attached to the objects we can ask what</subtitle>
<subtitle id='01:58:22'>is it like if one object is viewing another</subtitle>
<subtitle id='01:58:30'>the first question I just should ask everybody this is absurdly simple once</subtitle>
<subtitle id='01:58:37'>once you see it but the first question is when should I not be viewing the</subtitle>
<subtitle id='01:58:42'>object when it's in transition right so</subtitle>
<subtitle id='01:58:49'>it means I have to have at least a two-phase clock so the object really has</subtitle>
<subtitle id='01:58:58'>two two states it's going in one is it's trying to settle itself to what it</subtitle>
<subtitle id='01:59:02'>thinks as a stable state and the other one is one that's going to allow itself</subtitle>
<subtitle id='01:59:06'>to be viewed okay so mmm let's we can do that and</subtitle>
<subtitle id='01:59:11'>it's sort of a sort of a diagram here</subtitle>
<subtitle id='01:59:19'>so here's the here's the object and</subtitle>
<subtitle id='01:59:23'>here's the view so what we're saying is</subtitle>
<subtitle id='01:59:27'>that when the object is computing we can't view and when the object is</subtitle>
<subtitle id='01:59:34'>viewing we can't compute</subtitle>
<subtitle id='01:59:45'>so we're gonna have a bunch of these little phases like this now that's not</subtitle>
<subtitle id='01:59:53'>always useful sometimes this viewing</subtitle>
<subtitle id='01:59:58'>thing is very long so the viewing can</subtitle>
<subtitle id='02:00:02'>actually hold up the progress of the computation and so what can we do there</subtitle>
<subtitle id='02:00:11'>this is suggested by actually this model so far just just curious to see if it</subtitle>
<subtitle id='02:00:16'>suggests anybody what would be a good thing to do if to break this rigid</subtitle>
<subtitle id='02:00:22'>synchrony we have what can you do yeah</subtitle>
<subtitle id='02:00:27'>we could that's what's called slippage so we could actually arrange a slippage</subtitle>
<subtitle id='02:00:32'>model so we let the as before as we had</subtitle>
<subtitle id='02:00:37'>before we let the object compute and</subtitle>
<subtitle id='02:00:41'>what we take is a copy of it that we let</subtitle>
<subtitle id='02:00:47'>the viewer view</subtitle>
<subtitle id='02:00:54'>and so the object in simulation can have an quite a number of phases as it goes</subtitle>
<subtitle id='02:01:00'>along and every once in a while we get</subtitle>
<subtitle id='02:01:07'>to view it</subtitle>
<subtitle id='02:01:13'>we take let's say we take this guy right here okay now what's interesting is in</subtitle>
<subtitle id='02:01:20'>an object-oriented system this slippage model is usually computed automatically</subtitle>
<subtitle id='02:01:25'>by the the object in the view both of</subtitle>
<subtitle id='02:01:29'>which are objects when you hook the view up to the object what they do is</subtitle>
<subtitle id='02:01:34'>exchange information because one of the things that the object has some sense about is how long it takes it to settle</subtitle>
<subtitle id='02:01:40'>it state typically the view has some sense about how long it takes to</subtitle>
<subtitle id='02:01:44'>abstract the view and so they actually arrange and build a little buffer in</subtitle>
<subtitle id='02:01:53'>between themselves and that buffer has the actual amount of information to</subtitle>
<subtitle id='02:01:59'>allow the slippage to happen so the way this intertwines with doing real-time</subtitle>
<subtitle id='02:02:03'>and deterministic computing is almost all real-time solutions to queuing</subtitle>
<subtitle id='02:02:12'>problems knowing some sort of determinism they actually aren't</subtitle>
<subtitle id='02:02:16'>completely deterministic what you usually do is you're saying I have some</subtitle>
<subtitle id='02:02:20'>limits that I want to guarantee the</subtitle>
<subtitle id='02:02:25'>computation is going to take place in between it I'm going to do enough buffering to make sure that those limits</subtitle>
<subtitle id='02:02:30'>get down so for instance when you're doing real-time reading of records from</subtitle>
<subtitle id='02:02:36'>Fast disks and so forth you set up buffer areas because you don't want to</subtitle>
<subtitle id='02:02:42'>have to have real kind time constraints in every part of your real time</subtitle>
<subtitle id='02:02:47'>computation in an object-oriented system these are usually handled by having</subtitle>
<subtitle id='02:02:54'>what's called a viewing model small talk has one called models views and</subtitle>
<subtitle id='02:02:58'>controllers which is quite general and has the facilities in it for generating</subtitle>
<subtitle id='02:03:03'>all manner of slippage models in between by you putting on the outside what it is</subtitle>
<subtitle id='02:03:09'>that you actually need to know from these objects at some point of course</subtitle>
<subtitle id='02:03:13'>you can break it down there's no real time system you cannot break down but</subtitle>
<subtitle id='02:03:18'>this gives you the maximum amount of automatic buffering that the system can</subtitle>
<subtitle id='02:03:22'>generate without having to be explicitly programmed</subtitle>
<subtitle id='02:03:27'>yeah very very large how can you well</subtitle>
<subtitle id='02:03:51'>the way that's usually done is by trying to again it's that you know the stuff</subtitle>
<subtitle id='02:03:57'>isn't a panacea but what you usually try and do is when you write a device driver</subtitle>
<subtitle id='02:04:04'>in an object-oriented language what you try and do is ask what devices are</subtitle>
<subtitle id='02:04:09'>likely to be like this device now what is this like so when you write when</subtitle>
<subtitle id='02:04:17'>people do a user interface and an object-oriented language usually they</subtitle>
<subtitle id='02:04:21'>don't write a driver for the mouse or for a tablet or anything else what they</subtitle>
<subtitle id='02:04:25'>come up with is an abstraction of what it means to it's usually call a pick</subtitle>
<subtitle id='02:04:30'>device it's an abstraction of what it means to be able to do selection and</subtitle>
<subtitle id='02:04:35'>tracking and then one programmer at one</subtitle>
<subtitle id='02:04:39'>time writes code for that and then if you come up in a system and it has a</subtitle>
<subtitle id='02:04:44'>specific device you may have to write a line or two of additional code but it's</subtitle>
<subtitle id='02:04:48'>written in a subclass below that the main driver is already written already</subtitle>
<subtitle id='02:04:52'>been written in it's um it's not just doesn't just serve as the code for what</subtitle>
<subtitle id='02:04:56'>you're doing it serves as the model for how you treat the actual devices when</subtitle>
<subtitle id='02:05:01'>they're put in there so I'm part of the part of the the charm of the system is</subtitle>
<subtitle id='02:05:07'>to be able to get away from the from the particular as much as possible and</subtitle>
<subtitle id='02:05:13'>program as much as possible in the general case the whole act of</subtitle>
<subtitle id='02:05:20'>subclassing is basically saying to something I want something just like you accept and the theory behind this which</subtitle>
<subtitle id='02:05:28'>seems to work is that it is much easier to program differentially than it is to</subtitle>
<subtitle id='02:05:32'>program from scratch it's much easier if you see something that is like what you</subtitle>
<subtitle id='02:05:36'>want and you can get it in a way that um doesn't damage anything</subtitle>
<subtitle id='02:05:42'>else then if all you could make have to make as incremental changes to it then</subtitle>
<subtitle id='02:05:47'>you should be way ahead that's not always true you know there are always</subtitle>
<subtitle id='02:05:53'>pathological cases always pathological cases but generally speaking like this</subtitle>
<subtitle id='02:05:58'>is an example where the whole strategy once it was thought out was realized oh</subtitle>
<subtitle id='02:06:04'>yeah this is something we can use it's not just for user interfaces we can use it for every kind of device drivers we</subtitle>
<subtitle id='02:06:09'>can use it for every kind of real-time stuff where we have two different clocks</subtitle>
<subtitle id='02:06:14'>going at two different rates and we're trying to synchronize in some way why</subtitle>
<subtitle id='02:06:18'>should we have to write this over and over again why should some program we have to figure it out over and over</subtitle>
<subtitle id='02:06:23'>again it's not that we have the solution to every possible problem but what we're saying is we've got a solution it's the</subtitle>
<subtitle id='02:06:29'>80/20 rule get a solution to the eightieth you know 80% of all of the</subtitle>
<subtitle id='02:06:34'>code you're ever going to have to write if you can put that into a superclass</subtitle>
<subtitle id='02:06:39'>and then distribute it automatically as part of the solution so small so small</subtitle>
<subtitle id='02:06:43'>that when you when you're doing a viewing operation and small talk you</subtitle>
<subtitle id='02:06:48'>don't even have to think to yourself whether you should worry about</subtitle>
<subtitle id='02:06:52'>synchronization or not until long after</subtitle>
<subtitle id='02:06:56'>you may decide that you need it then you just have it oh it's already in here I just got it for free when I subclass the</subtitle>
<subtitle id='02:07:01'>class view well try think like I say an</subtitle>
<subtitle id='02:07:06'>ADA it's a little bit harder because you can't do those super classes that have</subtitle>
<subtitle id='02:07:10'>all those goodies lying in there you have to you can do it with a macro</subtitle>
<subtitle id='02:07:14'>operation people do to super classing and ADA by making macros that allow them</subtitle>
<subtitle id='02:07:21'>to do a kind of copying and stuff</subtitle>
<subtitle id='02:07:48'>No well in small talk no you can small</subtitle>
<subtitle id='02:07:53'>talk allows you to dynamic basically small talk has no concept of loading</subtitle>
<subtitle id='02:07:59'>code so everything is there dynamically into there and at any point</subtitle>
<subtitle id='02:08:05'>you can go in examine any piece of code in the system you can rewrite any piece</subtitle>
<subtitle id='02:08:09'>of code in a production case you really don't want to allow just anybody to go</subtitle>
<subtitle id='02:08:15'>in and rewrite a superclass because of</subtitle>
<subtitle id='02:08:19'>course the work it's really bad if they if the superclass starts doing something</subtitle>
<subtitle id='02:08:24'>different generally when people go to rewrite a super classes to improve the algorithm</subtitle>
<subtitle id='02:08:29'>that hundreds of applications are already using like you may go in and</subtitle>
<subtitle id='02:08:34'>improve the sort algorithm yeah</subtitle>
<subtitle id='02:08:51'>right that's why I was talking about the</subtitle>
<subtitle id='02:08:55'>configuration so my belief is that in a production case you must have something</subtitle>
<subtitle id='02:09:00'>like the configuration setup or else</subtitle>
<subtitle id='02:09:05'>it's just too fragile it's not it's it's</subtitle>
<subtitle id='02:09:09'>fragile in a funny way because in small talk we used to give $5 bills away to</subtitle>
<subtitle id='02:09:15'>anybody who could crash the Smalltalk system it's very hard to crash an a good</subtitle>
<subtitle id='02:09:21'>object-oriented system because there isn't anything you can get to that where you can actually hurt more than one</subtitle>
<subtitle id='02:09:26'>layer of thing and then the system's says hey wait a minute what are you</subtitle>
<subtitle id='02:09:30'>doing like in the small talk debugger as</subtitle>
<subtitle id='02:09:34'>you'll discover I think there's a tutorial coming up has the anytime</subtitle>
<subtitle id='02:09:38'>there's any kind of an error the system</subtitle>
<subtitle id='02:09:42'>doesn't crash there was there's no concept of crashing the error is simply</subtitle>
<subtitle id='02:09:47'>set aside as just another process and once when we were debugging the system</subtitle>
<subtitle id='02:09:52'>we found 1,700 suspended errors waiting</subtitle>
<subtitle id='02:09:57'>for somebody to take care of them and so I'll talk didn't care you know it's just an error comes up fine you know um set</subtitle>
<subtitle id='02:10:04'>it aside it's right there you can go back to it anytime you want but keep on running it just keeps on running so the</subtitle>
<subtitle id='02:10:11'>that's one of the reasons why we didn't do a configuration language because we</subtitle>
<subtitle id='02:10:15'>were programming in the small and you couldn't hurt yourself so as the the worst he could have</subtitle>
<subtitle id='02:10:20'>happened was something annoying they would come up but it wouldn't crash what</subtitle>
<subtitle id='02:10:25'>you're doing so somebody who fixed it or make a note of it but I think that's</subtitle>
<subtitle id='02:10:29'>intolerable in the production sense</subtitle>
<subtitle id='02:10:33'>where you really don't well you have people who aren't part of the same group</subtitle>
<subtitle id='02:10:38'>and so forth that you really have to have a configurations language and the super classes are the ones that you want</subtitle>
<subtitle id='02:10:43'>to have most understood and most nailed down in particular the for instance in</subtitle>
<subtitle id='02:10:53'>small talk it's often to make things like the sorting stuff parametric so</subtitle>
<subtitle id='02:11:00'>you're actually sending in sorting objects that will do sorting for you</subtitle>
<subtitle id='02:11:05'>as parameters rather than even putting</subtitle>
<subtitle id='02:11:09'>that in embedding that into the the code just because you don't want somebody to</subtitle>
<subtitle id='02:11:13'>try and change it that way you'd rather have it be something separate that you</subtitle>
<subtitle id='02:11:17'>can dynamically bind in really good superclasses don't do much except act as</subtitle>
<subtitle id='02:11:23'>really good binding mechanisms for other</subtitle>
<subtitle id='02:11:27'>stuff that's going on</subtitle>
<subtitle id='02:11:39'>yeah</subtitle>
<subtitle id='02:11:43'>yes there is you can but again the the</subtitle>
<subtitle id='02:11:48'>original the original small talk for example didn't use a kind of procedure</subtitle>
<subtitle id='02:11:53'>call in order to send it really acted as</subtitle>
<subtitle id='02:11:57'>though you're on a network and if you're interested in what order things had to</subtitle>
<subtitle id='02:12:03'>be done in they they could actually be stamped and recued at the other end and</subtitle>
<subtitle id='02:12:09'>people do do that when when you run small talk over the network people make</subtitle>
<subtitle id='02:12:15'>the connection to the network by having what are called phantom objects and a</subtitle>
<subtitle id='02:12:20'>phantom object is a stand-in from the object you're trying to send the net right because you're always sending a</subtitle>
<subtitle id='02:12:24'>message to something so suppose yours suppose your</subtitle>
<subtitle id='02:12:39'>so if you're over here and you think</subtitle>
<subtitle id='02:12:45'>you're sending a message what you think you're doing is sending a message from</subtitle>
<subtitle id='02:12:49'>object a to object B and but they may be</subtitle>
<subtitle id='02:12:53'>on different machines and so what may be really going on is object a is sending a</subtitle>
<subtitle id='02:13:01'>version of object B</subtitle>
<subtitle id='02:13:11'>which is really going over the network to the real be again these are called</subtitle>
<subtitle id='02:13:18'>Panem objects and usually there's just one class of them and whatever you're</subtitle>
<subtitle id='02:13:24'>distributing a copy a computation usually the environment for the objects</subtitle>
<subtitle id='02:13:31'>just consists of a few local objects and</subtitle>
<subtitle id='02:13:35'>the rest of them are phantom objects the phantom objects take care of all the the network stuff and synchronizations and</subtitle>
<subtitle id='02:13:43'>reorderings and other kinds of things that you have to do when you're going to slower slower media that's a</subtitle>
<subtitle id='02:13:49'>well-established technique and any good object-oriented language you can set</subtitle>
<subtitle id='02:13:53'>that up literally in an afternoon today</subtitle>
<subtitle id='02:13:57'>oh it's quite instructive to think about what it means not to send just a message</subtitle>
<subtitle id='02:14:02'>but to send an object from one place to another what part of its environment do you have to bring along with it in order</subtitle>
<subtitle id='02:14:08'>for it to be understood see in theory sending an object let's say we send</subtitle>
<subtitle id='02:14:14'>objects see across</subtitle>
<subtitle id='02:14:20'>well si may not be terribly understood</subtitle>
<subtitle id='02:14:24'>on the other side on the other hand it's still active so if your network has the</subtitle>
<subtitle id='02:14:31'>rule as ours did it park that whatever an object shows up and its class isn't</subtitle>
<subtitle id='02:14:36'>there its class a clone of its class</subtitle>
<subtitle id='02:14:40'>gets sucked over with it so you compare</subtitle>
<subtitle id='02:14:44'>that to sending a data structure which is sending bits and how fragile they are</subtitle>
<subtitle id='02:14:50'>because you're not sure that there are procedures at the other end to know them here you're ensuring that either nothing</subtitle>
<subtitle id='02:14:55'>at all happens or the right procedures are actually automatically sent along</subtitle>
<subtitle id='02:14:59'>and so you can it's remember that story I told the beginning of the Vosges 220</subtitle>
<subtitle id='02:15:04'>that's exactly how the training command protected their their tapes you just</subtitle>
<subtitle id='02:15:09'>make sure the procedures go along with them and it's quite easy using these</subtitle>
<subtitle id='02:15:13'>phantom objects to make that automatic so you can think of the network of</subtitle>
<subtitle id='02:15:18'>objects as constantly rebalancing itself as to where the code actually is</subtitle>
<subtitle id='02:15:35'>I think I believe that's true and from</subtitle>
<subtitle id='02:15:42'>Park yeah it's written it's been written up</subtitle>
<subtitle id='02:15:49'>yeah well my message to you is this is the same reason I told you the Arthur</subtitle>
<subtitle id='02:15:53'>Andersen story is they have exactly the same you know their their attitude to me</subtitle>
<subtitle id='02:16:01'>was kind of interesting they said they went to several phases and this is</subtitle>
<subtitle id='02:16:05'>probably you're in one of these phases right now as well it went through one</subtitle>
<subtitle id='02:16:09'>phase where the first phase with objects it was like magic God all the things you</subtitle>
<subtitle id='02:16:14'>could do code is so small the second phase was complete disillusionment when</subtitle>
<subtitle id='02:16:19'>they realize that for instance small talk which they were using as a model</subtitle>
<subtitle id='02:16:23'>didn't scale they said you know what is you know is this the emperor's new</subtitle>
<subtitle id='02:16:28'>clothes or what and I said no it's just because the part of the reason small</subtitle>
<subtitle id='02:16:34'>talk wasn't built to scale was simply because we were able to do an enormous</subtitle>
<subtitle id='02:16:39'>amount with very tiny programs and we're</subtitle>
<subtitle id='02:16:43'>designing for children anyway and when</subtitle>
<subtitle id='02:16:47'>you want to use these ideas and they're in the in the large I believe that you</subtitle>
<subtitle id='02:16:51'>have to do a little bit more then you can go out on the street and buy that's</subtitle>
<subtitle id='02:16:55'>what I'm my message to you is that and</subtitle>
<subtitle id='02:17:00'>it was to Arthur Anderson that you know a lot about what it can once you've</subtitle>
<subtitle id='02:17:05'>learned the object-oriented style which I believe is the right way a protecting</subtitle>
<subtitle id='02:17:09'>state of the right way of making components the right way of making urns</subtitle>
<subtitle id='02:17:14'>superclasses right way of sharing there's a whole bunch of right things about it in order to make it work in the</subtitle>
<subtitle id='02:17:20'>large you then have to sit down and protect that by coming up with a</subtitle>
<subtitle id='02:17:25'>configuration language and you can do yourself a lot of good by doing that</subtitle>
<subtitle id='02:17:30'>carefully because the configuration language can include languages that you</subtitle>
<subtitle id='02:17:34'>already have hundreds of programmers that know how to write in in other words</subtitle>
<subtitle id='02:17:39'>the configuration language can be a way of protecting programs that are already</subtitle>
<subtitle id='02:17:44'>written in COBOL and Fortran as well as</subtitle>
<subtitle id='02:17:48'>new programs written in Ada it should be a really separate way you think of isn't</subtitle>
<subtitle id='02:17:52'>and the architecture is opposed to the bricks of actually building the thing</subtitle>
<subtitle id='02:17:57'>the architecture to me rules life is an architecture it wasn't</subtitle>
<subtitle id='02:18:02'>as early as the turn of the century there are people that thought memory there's the stuff called protoplasm</subtitle>
<subtitle id='02:18:07'>written about in books was supposed to</subtitle>
<subtitle id='02:18:11'>be some special kind of material that you can build living things out of because people didn't believe that</subtitle>
<subtitle id='02:18:16'>ordinary chemicals could bake you could make a living thing out of it wasn't</subtitle>
<subtitle id='02:18:21'>really until 20 or 30 years ago that it was really shown quite definitively that</subtitle>
<subtitle id='02:18:28'>we actually are just an architecture in fact we know now that the atoms in our</subtitle>
<subtitle id='02:18:33'>body are actually recycled about every seven years so you and I as individuals</subtitle>
<subtitle id='02:18:39'>are patterns in space the material is moving through we don't have the same</subtitle>
<subtitle id='02:18:45'>atoms in our bodies that we had seven years ago we are a pattern and</subtitle>
<subtitle id='02:18:50'>interesting things made out of the patterns you have - you know I have to</subtitle>
<subtitle id='02:18:55'>have some understanding of the bricks and stuff which I think everybody is getting now but at some point you'll</subtitle>
<subtitle id='02:19:00'>realize that the power of this stuff isn't from what the bricks do and that</subtitle>
<subtitle id='02:19:04'>the bricks are have integrity the power</subtitle>
<subtitle id='02:19:08'>of the stuff is from the architectures that you can create and the</subtitle>
<subtitle id='02:19:12'>architectures have just been scratched now up until really a couple of years</subtitle>
<subtitle id='02:19:19'>ago there probably been less than a god I don't know 100 or 200 people over two</subtitle>
<subtitle id='02:19:24'>decades actually doing this stuff so</subtitle>
<subtitle id='02:19:28'>it's the and the problems that have been</subtitle>
<subtitle id='02:19:32'>worked on have tended to be small the reason I believe that object-oriented</subtitle>
<subtitle id='02:19:36'>programming works well in the large is simply because it works well in the</subtitle>
<subtitle id='02:19:40'>biological world and I see no reason why it is going to fall down in any way when</subtitle>
<subtitle id='02:19:46'>we go large but in order to in order to make it work we have to either look at</subtitle>
<subtitle id='02:19:51'>the biological world war which is the</subtitle>
<subtitle id='02:19:55'>biological reason of urging can a configuration language or we have to go</subtitle>
<subtitle id='02:19:59'>after for other reasons of just realizing hey this stuff gets fragile at</subtitle>
<subtitle id='02:20:03'>this point what do we actually need and the answer is a configuration language</subtitle>
<subtitle id='02:20:14'>but I think that there might be some immediate benefit these ideas of</subtitle>
<subtitle id='02:20:20'>object-oriented design where you have existing systems that because it would</subtitle>
<subtitle id='02:20:26'>nature the islands of automation approach have gotten tremendous ly complex and you</subtitle>
<subtitle id='02:20:32'>need to be able to characterize various things possibly the concept of objects</subtitle>
<subtitle id='02:20:38'>to help you do that and to help them understand what are the objects of one</subtitle>
<subtitle id='02:20:43'>of the Linc right well I'm trying to think of it was</subtitle>
<subtitle id='02:20:51'>Rudolph's irken that said you can't if you want to be a piano player you should</subtitle>
<subtitle id='02:20:55'>spend half of your time reading books and his his point was is that if you</subtitle>
<subtitle id='02:21:02'>spend all of your time just learning to move your fingers you have not absorbed</subtitle>
<subtitle id='02:21:07'>any contact the context necessary to play any real piece of music that</subtitle>
<subtitle id='02:21:11'>there's there's something else besides the practical application of the of the</subtitle>
<subtitle id='02:21:16'>technique and I think that the somebody was asking me at the break it was a very</subtitle>
<subtitle id='02:21:21'>good question actually which is and the</subtitle>
<subtitle id='02:21:26'>it had to do with she doesn't sounds</subtitle>
<subtitle id='02:21:30'>like objects make you do a lot of design and anyway but you know it wasn't said</subtitle>
<subtitle id='02:21:37'>stupidly at all it's just said isn't that hard and I said yes it is hard and</subtitle>
<subtitle id='02:21:43'>it's hard whether you've got objects or not the main reason is that objects</subtitle>
<subtitle id='02:21:48'>provide both an excuse for designing and they also give you a framework for</subtitle>
<subtitle id='02:21:52'>holding the design every little bit of design you do you get rewarded in an</subtitle>
<subtitle id='02:21:57'>object-oriented system for having done it you really get rewarded where's it's</subtitle>
<subtitle id='02:22:02'>hard to get rewarded in a in a procedure data structure system because often the</subtitle>
<subtitle id='02:22:07'>design has nothing to hang itself on there can be local good things but you</subtitle>
<subtitle id='02:22:12'>can't propagate the design forward the way you can in an object-oriented system</subtitle>
<subtitle id='02:22:21'>I don't know because I haven't hung most</subtitle>
<subtitle id='02:22:25'>you know Edward de Bono's says the problem with most American companies is</subtitle>
<subtitle id='02:22:29'>that when they get in trouble they redouble their efforts so you know the</subtitle>
<subtitle id='02:22:36'>idea is that we're basically too industrious for our own good and once we learn a technique we tend to put our</subtitle>
<subtitle id='02:22:41'>head down and just fight like mad rather than trying to smart our way out of it</subtitle>
<subtitle id='02:22:45'>like I said I particularly efference to</subtitle>
<subtitle id='02:22:49'>me I had actually seen these techniques and actually programs using some of these techniques for five years for a</subtitle>
<subtitle id='02:22:54'>period between 1961 and 1966 before</subtitle>
<subtitle id='02:23:01'>Simula hit me on the head and hit me on the head just because at that point I</subtitle>
<subtitle id='02:23:06'>had a problem that was much harder than I wanted to program it was the first</subtitle>
<subtitle id='02:23:10'>time I was willing to actually see that was when I was going through insane</subtitle>
<subtitle id='02:23:14'>minutes and I said to myself holy cow this is so you know there's just nothing</subtitle>
<subtitle id='02:23:20'>here all I have to do is this and that I'm done you know all of these things</subtitle>
<subtitle id='02:23:25'>fall in I was actually programmed in the game of space war you know which is one</subtitle>
<subtitle id='02:23:30'>of the first video games but it wasn't even a video game back in the in the 60s</subtitle>
<subtitle id='02:23:34'>and they're all of these it's very hard to do in an ordinary language because you have all of these spaceships and you</subtitle>
<subtitle id='02:23:39'>have planets and you have torpedoes and when I was looking at Simula I was</subtitle>
<subtitle id='02:23:44'>trying to get figure a way out of doing</subtitle>
<subtitle id='02:23:48'>this I didn't want to do it in 30 pages of alcohol or so and I was trying to</subtitle>
<subtitle id='02:23:53'>figure out a way and all of a sudden it occurred to me that every single thing in space war and Simula was the same</subtitle>
<subtitle id='02:23:59'>thing the only thing was different was the costume they were wearing the</subtitle>
<subtitle id='02:24:03'>planets were the same the spaceships were the same the torpedoes were the</subtitle>
<subtitle id='02:24:07'>same there was like one line of code difference in each of their behavior and</subtitle>
<subtitle id='02:24:11'>they all had to obey Newton's laws they all were interacting with each others in</subtitle>
<subtitle id='02:24:15'>exactly the same way it was trivial and I wrote that program and a half a page</subtitle>
<subtitle id='02:24:19'>of code and I never looked back since because the you know the that is the</subtitle>
<subtitle id='02:24:25'>thing if you don't find this folding up of complexity into simplicity then</subtitle>
<subtitle id='02:24:32'>either you're working on a truly hard problem which really really do exist</subtitle>
<subtitle id='02:24:38'>or there's probably a rotation of the situation that you haven't examined yet</subtitle>
<subtitle id='02:24:43'>you're probably still thinking the old way in thinking in terms of particulars</subtitle>
<subtitle id='02:24:48'>rather than generalities we're so used to programming up each specific thing</subtitle>
<subtitle id='02:24:52'>that's hard for us to think of avoiding that then we only have to to program up</subtitle>
<subtitle id='02:24:57'>one general thing and then write a couple of lines of code for each of the</subtitle>
<subtitle id='02:25:01'>particulars and we're done that's a really good test in this stuff and it</subtitle>
<subtitle id='02:25:07'>accounts for the religious fervor of people who have had this happen to</subtitle>
<subtitle id='02:25:11'>themselves as after pounding your head away on a system to have it fold up like</subtitle>
<subtitle id='02:25:15'>like there was nothing there it is the most amazing thing they have an</subtitle>
<subtitle id='02:25:20'>operating system go away to something that is practically a clock which is</subtitle>
<subtitle id='02:25:25'>what it is in an object-oriented system because what do you need in an operating system well once you've got the ability</subtitle>
<subtitle id='02:25:30'>to sustain objects and stuff like that you practically only need a clock you</subtitle>
<subtitle id='02:25:34'>only need to get control routed around and everything else is written essentially as an application on top of</subtitle>
<subtitle id='02:25:40'>that kernel that's a very modern way of looking at things and it's a terrific</subtitle>
<subtitle id='02:25:44'>way of thinking about doing stuff</subtitle>
<subtitle id='02:25:56'>okay yeah</subtitle>
<subtitle id='02:26:00'>that's a very good question some of these idea a relational database</subtitle>
<subtitle id='02:26:08'>everybody knows what a relational database is right okay so the the there</subtitle>
<subtitle id='02:26:16'>are several things a relational data an item in a relational database has fields</subtitle>
<subtitle id='02:26:24'>it has some of some of the things and depending on the data dictionary that</subtitle>
<subtitle id='02:26:28'>the relational database wants to sustain you can occasionally do some integrity</subtitle>
<subtitle id='02:26:33'>constraints the most relational database is friend for example is very difficult</subtitle>
<subtitle id='02:26:37'>to do the following thing in a data record and that is make sure that Joe</subtitle>
<subtitle id='02:26:42'>blows age is always the right one when you ask it because when you ask</subtitle>
<subtitle id='02:26:47'>somebody's age in a relational database what it expects to do is to go to a</subtitle>
<subtitle id='02:26:51'>field and find a number and bring it back to you right in an object system</subtitle>
<subtitle id='02:26:58'>what you would have there is you'd sent the message age to the object and it</subtitle>
<subtitle id='02:27:05'>could just go to a field and bring back a number but a smarter one would</subtitle>
<subtitle id='02:27:09'>actually look at the guy's birthdate and compute his age for you right then and</subtitle>
<subtitle id='02:27:15'>so you'd always get the right answer every time you asked aged you would</subtitle>
<subtitle id='02:27:19'>always get the right answer from the object you would not get it from the relational database unless you're doing</subtitle>
<subtitle id='02:27:24'>careful updates that's one difference</subtitle>
<subtitle id='02:27:28'>the other difference is that in a in a relate in any kind of a relation it is</subtitle>
<subtitle id='02:27:35'>extremely difficult to embed code although people sometimes do by</subtitle>
<subtitle id='02:27:39'>embedding it on the outside of the database rather than on the inside with</subtitle>
<subtitle id='02:27:44'>it so for doing a dynamic simulation for instance is quite difficult a good way</subtitle>
<subtitle id='02:27:49'>of understanding where relational databases is going to go comes out of</subtitle>
<subtitle id='02:27:53'>one of your own products and an industry that McDonnell Douglas is one of the</subtitle>
<subtitle id='02:27:58'>leaders in Amanda's CAD CAM CAD cam can't be done on relational straight</subtitle>
<subtitle id='02:28:05'>relational databases there simply aren't enough hooks in there to deal with all</subtitle>
<subtitle id='02:28:09'>the things it's not you can't store the data so you can't deal with all the</subtitle>
<subtitle id='02:28:13'>other things that the relational database database can't store that</subtitle>
<subtitle id='02:28:18'>cad/cam requires so object-oriented</subtitle>
<subtitle id='02:28:23'>servers like the gemstone or this the</subtitle>
<subtitle id='02:28:27'>ontological rated servers are ones that</subtitle>
<subtitle id='02:28:32'>the CAD cam industry is going towards now these allow you to do all the things</subtitle>
<subtitle id='02:28:36'>that you're used to doing with relational database but also give you this extra level of abstraction that you</subtitle>
<subtitle id='02:28:43'>get from objects what's nice about it I think for people worried about</subtitle>
<subtitle id='02:28:48'>transitions is that there's a fairly reasonable transition almost everything gets better when you go to an</subtitle>
<subtitle id='02:28:53'>object-oriented database server for instance I think most people would like</subtitle>
<subtitle id='02:28:59'>for instance to have joins be real</subtitle>
<subtitle id='02:29:03'>things rather than a made-up thing for</subtitle>
<subtitle id='02:29:07'>the moment and they can be in an object-oriented database most people</subtitle>
<subtitle id='02:29:11'>would like to have views be things that you can add it back through or views</subtitle>
<subtitle id='02:29:15'>that you can view whereas a view in a</subtitle>
<subtitle id='02:29:19'>relational database is an extremely weak notion of the whole notion of what view</subtitle>
<subtitle id='02:29:24'>is where in an object-oriented system is extremely easy to have a view look like</subtitle>
<subtitle id='02:29:29'>the set of stuff itself and so you can put another view on top of it and</subtitle>
<subtitle id='02:29:33'>cascade them and so forth and all of those things are being done right at</subtitle>
<subtitle id='02:29:38'>this moment with object-oriented servers</subtitle>
<subtitle id='02:29:47'>excuse me yeah I think for also because</subtitle>
<subtitle id='02:29:59'>the the tutorial it's going to happen in a couple of weeks is going to be one of the people from this digital company the</subtitle>
<subtitle id='02:30:05'>company that does small talk V I want to just mention again that besides the fact</subtitle>
<subtitle id='02:30:12'>that it's cheap small talk V I think is only $99 on the IBM PC and 150 on the</subtitle>
<subtitle id='02:30:18'>Mac so it's the cheapest small talk they have by far the best manual none of the</subtitle>
<subtitle id='02:30:24'>other manuals are even in second place because they actually don't believe that</subtitle>
<subtitle id='02:30:30'>you understand about object-oriented programming in the beginning of the</subtitle>
<subtitle id='02:30:34'>thing they actually write the manual there's a splendid tutorial hands-on tutorial for getting versed with all of</subtitle>
<subtitle id='02:30:40'>the object-oriented lore and sub-classing and building a very</subtitle>
<subtitle id='02:30:45'>powerful little application another thing that they give you for free in</subtitle>
<subtitle id='02:30:51'>with small talk I don't have any stock in the company I haven't made a cent on</subtitle>
<subtitle id='02:30:56'>small talk but what they do is they also</subtitle>
<subtitle id='02:31:00'>give you for free a full-blown implementation of Prolog Edinboro Prolog</subtitle>
<subtitle id='02:31:06'>written in small talk okay and just to</subtitle>
<subtitle id='02:31:13'>give you an idea this whole implementation of Prolog written in small talk with its own user interface</subtitle>
<subtitle id='02:31:17'>its own browser its own debugger and everything else is less than 20 pages of</subtitle>
<subtitle id='02:31:21'>code okay and if you've ever tried doing</subtitle>
<subtitle id='02:31:25'>anything like a programming language like this is a convince err okay and it</subtitle>
<subtitle id='02:31:30'>uses object-oriented programming for what it's really it uses the fact for</subtitle>
<subtitle id='02:31:35'>instance in small talk everything is an object everything is an object and</subtitle>
<subtitle id='02:31:40'>protected including the things that you think of as stack frames and ordinary</subtitle>
<subtitle id='02:31:44'>languages that you can't even get to how is it the bugger written in small talk</subtitle>
<subtitle id='02:31:48'>well this stack frame is simply an object so you simply write a method that</subtitle>
<subtitle id='02:31:53'>allows you to ask the guy well what do you what do you have here what do you</subtitle>
<subtitle id='02:31:57'>have here can you advance your PC what see I mean I mean the debugger is like a</subtitle>
<subtitle id='02:32:03'>page and a half long because it actually is part of it's just a subclass of class</subtitle>
<subtitle id='02:32:09'>stack frame prologue is so simple in small type because they actually take</subtitle>
<subtitle id='02:32:14'>the stack frame as an object and implement prologues control structure</subtitle>
<subtitle id='02:32:19'>directly in using the small talk using</subtitle>
<subtitle id='02:32:23'>small talk sone stack frames but using a non stack protocol which is what the</subtitle>
<subtitle id='02:32:28'>Prolog backtracking requires this is gorgeous stuff and it's done completely</subtitle>
<subtitle id='02:32:32'>without impinging on the integrity of</subtitle>
<subtitle id='02:32:36'>small talk itself the two systems are integrated together and so you can do</subtitle>
<subtitle id='02:32:41'>Prolog unifications into small talk variables and vice versa so it's a</subtitle>
<subtitle id='02:32:47'>perfect example of what an embedded system in an object-oriented system looks like they give it to you for free</subtitle>
<subtitle id='02:32:52'>you can do real work in it if you just want to use it but people are really</subtitle>
<subtitle id='02:32:56'>interested in why this stuff is powerful that's an example of where the power of</subtitle>
<subtitle id='02:33:02'>it is actually concentrated and used by some design thinking here's another one</subtitle>
<subtitle id='02:33:08'>most object-oriented languages don't</subtitle>
<subtitle id='02:33:12'>have a complete model so for instance</subtitle>
<subtitle id='02:33:16'>when Simula for instance has classes so</subtitle>
<subtitle id='02:33:21'>you have a class paragraph or a class</subtitle>
<subtitle id='02:33:25'>string but Simula doesn't have classes</subtitle>
<subtitle id='02:33:29'>be objects so if you have an object-oriented one of the choices you</subtitle>
<subtitle id='02:33:34'>could make is to have everything in the language be an object why not that means</subtitle>
<subtitle id='02:33:38'>if there are things called classes there</subtitle>
<subtitle id='02:33:42'>must be a class class a class whose instances are the classes okay that</subtitle>
<subtitle id='02:33:50'>sound shaky let me just let me just draw it cuz it's</subtitle>
<subtitle id='02:34:09'>so I'm going to draw classes in red so</subtitle>
<subtitle id='02:34:15'>this might be integer might be fraction</subtitle>
<subtitle id='02:34:21'>might be paragraph this might be document this might be file and there</subtitle>
<subtitle id='02:34:29'>are instances I'll draw in green this might be three and this might be for</subtitle>
<subtitle id='02:34:34'>this might be three quarters this is a</subtitle>
<subtitle id='02:34:40'>paragraph of text and so is this one</subtitle>
<subtitle id='02:34:44'>this is a whole document this is a whole file here's another one they have lots</subtitle>
<subtitle id='02:34:51'>of instances of these classes they've been on Simula these red things in an</subtitle>
<subtitle id='02:34:56'>ADA these red things aren't around at runtime they're like macros they just help</subtitle>
<subtitle id='02:35:02'>create the structures underneath that these green guys can work with but in</subtitle>
<subtitle id='02:35:07'>small talk these are really objects and</subtitle>
<subtitle id='02:35:11'>the question is is if they're objects what are they an instance of what is</subtitle>
<subtitle id='02:35:16'>common to all of these things somebody tell me they're all a class so</subtitle>
<subtitle id='02:35:23'>what what's common to all of these what do they do they all make instances right</subtitle>
<subtitle id='02:35:30'>I mean they're the thing that holds all of the information that's necessary to</subtitle>
<subtitle id='02:35:34'>make multiple instances and so you can imagine that there might be a thing</subtitle>
<subtitle id='02:35:39'>called class class whose own instances</subtitle>
<subtitle id='02:35:48'>are these guys</subtitle>
<subtitle id='02:35:55'>okay that sound reasonable why not okay</subtitle>
<subtitle id='02:36:03'>down remember I can subclass what do you</subtitle>
<subtitle id='02:36:08'>think it might mean to sub class class class let me do that let me use another</subtitle>
<subtitle id='02:36:16'>color here</subtitle>
<subtitle id='02:36:23'>so I'm going to sub class class class here look just in general what is the</subtitle>
<subtitle id='02:36:31'>sub class of class class going to be able to do it's going to no it's not</subtitle>
<subtitle id='02:36:36'>gonna make some classes it's gonna make be able to make classes like these guys</subtitle>
<subtitle id='02:36:40'>plus something else then I'm gonna add right there because anything that's of</subtitle>
<subtitle id='02:36:48'>class class is going to make classes so any subclass of it is going to make</subtitle>
<subtitle id='02:36:52'>classes now here's an example of something we did at parc many years ago</subtitle>
<subtitle id='02:36:57'>we wanted to do a system in which every</subtitle>
<subtitle id='02:37:02'>instance was data-driven okay in other</subtitle>
<subtitle id='02:37:06'>words we wanted to do a data flow system</subtitle>
<subtitle id='02:37:13'>inside of small talk in which the every</subtitle>
<subtitle id='02:37:17'>thing that happened to some variable in</subtitle>
<subtitle id='02:37:22'>an instance could be propagated to the next thing that meant that every instance had to have besides the places</subtitle>
<subtitle id='02:37:29'>in it that an ordinary instance has here's what an ordinary instance looks</subtitle>
<subtitle id='02:37:35'>like it's a thing that has slots in it for holding values and plus what we</subtitle>
<subtitle id='02:37:41'>wanted to do was to tack onto that some</subtitle>
<subtitle id='02:37:47'>pointer information that would link all of these guys together so we'd actually</subtitle>
<subtitle id='02:37:51'>have a data-driven network here now how do you suppose we</subtitle>
<subtitle id='02:37:56'>did that sub class class class</subtitle>
<subtitle id='02:38:02'>right the various places I could do that but what if I did it up here and put</subtitle>
<subtitle id='02:38:07'>that information in here and now every</subtitle>
<subtitle id='02:38:14'>every class that this guy makes whatever</subtitle>
<subtitle id='02:38:21'>it is is going to have the property that the instances of it regardless of what</subtitle>
<subtitle id='02:38:27'>these guys are as I go along making up new classes for this kind of thing and that kind of thing every one of them is</subtitle>
<subtitle id='02:38:32'>going to have the property that the instances are going to be instrumented this way see how high that change was</subtitle>
<subtitle id='02:38:37'>made what I did is I actually change the meaning of what class this was in the</subtitle>
<subtitle id='02:38:43'>system with one operation I just subclass a very very high-level guy and</subtitle>
<subtitle id='02:38:49'>all of a sudden I got essentially a new small talk with a completely different</subtitle>
<subtitle id='02:38:54'>strategy for how these things strategy independent of what the new classes are</subtitle>
<subtitle id='02:38:58'>going to be okay that's the power of</subtitle>
<subtitle id='02:39:02'>this stuff it's not the direct stuff</subtitle>
<subtitle id='02:39:06'>that you can do that's so appealing now it's the meta stuff that you can do</subtitle>
<subtitle id='02:39:10'>that's so incredibly powerful because you can literally when you have a new</subtitle>
<subtitle id='02:39:16'>idea that's important you can literally distribute that idea over the entire</subtitle>
<subtitle id='02:39:20'>universe with just a few changes in a</subtitle>
<subtitle id='02:39:24'>system like this well let's I think we're about done let</subtitle>
<subtitle id='02:39:28'>me let me give you a one of our favorite</subtitle>
<subtitle id='02:39:33'>stories and as a winch and Winston</subtitle>
<subtitle id='02:39:38'>Churchill story widget Winston Churchill jokes always have them at a party after</subtitle>
<subtitle id='02:39:44'>a bunch of whiskeys and I'm sure everybody knows the one of</subtitle>
<subtitle id='02:39:49'>the he was incredibly drunk and a woman</subtitle>
<subtitle id='02:39:53'>came up to him at two o'clock in the morning and said mr. Churchill you're</subtitle>
<subtitle id='02:39:57'>disgustingly drunk and he looked at her</subtitle>
<subtitle id='02:40:01'>said and you Madame are indescribably ugly but in the morning I'll be</subtitle>
<subtitle id='02:40:05'>indisputably sober</subtitle>
<subtitle id='02:40:11'>so this particular this particular Churchill joke a little earlier on the</subtitle>
<subtitle id='02:40:16'>party he hadn't had quite as many whiskey's and the hostess of the party</subtitle>
<subtitle id='02:40:20'>came over to him quite agitated and said mr. Churchill I'm just really upset I</subtitle>
<subtitle id='02:40:26'>don't know what to do I saw a famous Earl over there steal some of my silver</subtitle>
<subtitle id='02:40:32'>salt shakers what should I do Churchill thought for a minute and stuck his cigar in his mouth and went over to</subtitle>
<subtitle id='02:40:38'>the Earl along the way he took a salt shaker himself and put it in his pocket</subtitle>
<subtitle id='02:40:42'>and we got over to the Earl took it out of his pocket and said I think we've</subtitle>
<subtitle id='02:40:47'>been noticed perhaps we should put these back so that's my version for why we won</subtitle>
<subtitle id='02:40:54'>World War two in other words if you want to get people to do something to go</subtitle>
<subtitle id='02:41:00'>along with you you have to involve them in the same conspiracy and</subtitle>
<subtitle id='02:41:04'>object-oriented programming is a kind of conspiracy that people are just finding</subtitle>
<subtitle id='02:41:09'>out about it I hope I've been able to involve you in a little bit and I hope you will involve others thank you</subtitle>
<subtitle id='9674'>[Applause] </subtitle>