THE ORIGINS OF PATTERN THEORY THE FUTURE OF THE THEORY, AND THE GENERATION OF A LIVING WORLD

Christopher Alexander

Introduction by James O. Coplien

nce in a great while, a great idea makes it across the boundary of one discipline to take root in another. The adoption of Christopher O Alexander’s patterns by the software community is one such event. Alexander both commands respect and inspires controversy in his own discipline; he is the author of several books with long-running publication records, the first recipient of the AIA Gold Medal for Research, a member of the Swedish Royal Academy since 1980, a member of the American Academy of Arts and Sciences, recipient of dozens of awards and honors including the Best Building in Japan award in 1985, and the American Association of Collegiate Schools of Architecture Distinguished Professor Award. It is odd that his ideas should have found a home in software, a discipline that deals not with timbers and tiles but with pure thought stuff, and with ephemeral and weightless products called programs. The software community embraced the pattern vision for its relevance to problems that had long plagued software design in general and object-oriented design in particular.

September/October 1999 IEEE Software 71 Focusing on objects had caused us to lose the pattern discipline that the software community has system perspective. Preoccupation with design yet scarcely touched: the moral imperative to build method had caused us to lose the human perspec- whole systems that contribute powerfully to the tive. The curious parallels between Alexander’s quality of life, as we recognize and rise to the re- world of buildings and our world of software con- sponsibility that accompanies our position of influ- struction helped the ideas to take root and thrive in ence in the world. And that leads us to the third grassroots programming communities worldwide. inspiration for the direction of patterns in our disci- The pattern discipline has become one of the most pline: Christopher Alexander himself, who directly widely applied and important ideas of the past engaged our community in this keynote speech at decade in software architecture and design. OOPSLA ’96. The timing and audience of the venue We can trace the path of influence through three afforded Alexander the chance to reflect on his own primary sources. The first is the Design Patterns book work and on how the object-oriented programming by Gamma et al., a book that helped people con- community had both hit and missed the mark in ceptualize beyond individual design relationships adopting and adapting his ideas to software. As to grasp important structures of micro-architectures, such, the speech was a landmark event that raised and to value proven solution strategies over raw in- the bar for patterns advocates, for object-oriented novation. The second was the series of pattern con- programmers, and for software practitioners every- ferences (PLoPs) that provided a forum for pattern where. Beyond that, this speech has timeless rele- enthusiasts to support each other in creating a new vance to any engineering, scientific, or professional body of software literature. The PLoPs were also a endeavor. forum where the community could struggle with The following presentation was recorded live in growing from individual patterns to pattern lan- San Jose, California, USA, October 1996, at The 1996 guages that engender systems thinking. ACM Conference on Object-Oriented Programs, But growth into the deeper and more funda- Systems, Languages, and Applications (OOPSLA). mental aspects of patterns has been slow and diffi- * * * cult. And even as we struggle with the growth from “I’d like you all to very heartily welcome Professor patterns to pattern languages, there is a level of the Alexander as he addresses us.”

KEYNOTE ADDRESS BY CHRISTOPHER ALEXANDER

hank you very much. This is a some of the things that I’ve done. pretty strange situation I find my- When I faced the question of addressing you, I self in. I hope you sympathize wondered what on earth I should talk about. And, “T with me. I’m addressing a room earlier, a few months ago I faced a similar thing when full of people, a whole football I was asked to write an introduction to Richard field full of people. I don’t know hardly anything Gabriel’s book (Patterns of Software) and again the about what all of you do. So—please be nice to me. question for me was: What in the world should I write My association with you—if I can call it that— about? What is there that I could say that would be began, oh it must have been two or three years ago. of interest? And, because I, in a way, myself started I began getting calls from computer people. Then out in computers many years ago in the late ’50s, this somebody, a computer scientist, called me and said question became quite fascinating to me and quite that there were a group of people here in Silicon absorbing. But still, I wasn’t given much to go on. Valley that would pay $3000 to have dinner with me. Take Jim for example. When he invited me, he was I thought—what is this? It took me some time to find very friendly and I said to him, ‘Look, what do you out. I didn’t really understand what had been going want me to talk about?’and so forth. He said ‘Oh that on, and that my work had somehow been useful to doesn’t matter. Just talk about anything. Because it’s computer science. Only now I’m beginning to un- you, and because of the history of this pattern prob- derstand a little bit more of what you are doing in lem, people will find it interesting.’But still I thought, your field and the way in which it comes, in part, from What should I really talk about?

72 IEEE Software September/October 1999 What is the connection between what I am doing tect. All of my life I’ve spent trying to learn how to in the field of architecture and what you are doing produce living structure in the world. That means in computer science and trying to do in the new field towns, streets, buildings, rooms, gardens, places of software design? That is the question I must talk which are themselves living or alive. My assumption about. What I’ll do, in the time I’ve got here, is to tell here—a sad one—is that for the most part what we you where my thoughts went as I stepped through have been doing for ourselves, at least during the the invention of the pattern concept, and where I last 50 years or so, perhaps starting somewhere have gone since then. In addition, I shall reach a con- around World War II, has virtually no ability to pro- clusion which may surprise you. As I’ve been prepar- duce that kind of living structure in the world. This ing for this speech during the last few months, I living structure which is needed to sustain us and ended up with something that may startle you, and nurture us and which did exist to some degree in you may find quite strange. But, I’m not going to tell the traditional societies and in rural communities you what that is just yet. and in early urban settlements has disappeared. It In effect, I’m just going to do three things. is drastically gone. We don’t know how to create it 1. Pattern Theory. I’m going to talk first of all or generate it any more. about patterns and pattern languages, what I did Of course, especially for architects, that is a de- about that, a few little points about problems we batable matter. Some professional architects might encountered, why we did it, how we did it, and so say, What are you talking about? What we are doing forth. That is a historical survey referring back to the is absolutely fine, the buildings we are building today late ’60s and early ’70s. are excellent, very good, no problem!! I suppose the 2. The Nature of Order. Then, I’m going to sum- architect of this particular huge and nauseating con- marize the theoretical framework which has evolved ference hall we are in, here in San Jose, where we can out of the pattern work: a framework which is about hardly understand each other, would say that, too. to be published in a series of four books collectively But, actually, it isn’t fine. It’s a hell of a problem. It’s a called The Nature of Order, four books that will be put serious problem. It affects every man, woman, and out by Oxford University Press in the year 2000. That child on Earth. We are so ignorant about how to do framework is a fairly radical departure from what the this, to make living structure on Earth, it is lamenta- pattern language in the earlier theories contained, ble. And it is very, very serious, becomes more seri- although it is consistent with them. That’ll be the sec- ous every day, because the population of the Earth ond thing. And, I’ll just try and sketch that out in the is growing, and the Earth is being damaged more hope that there might be some carryover or you and more—and with the damage to our towns and might possibly find it interesting—even though of buildings, we too are being damaged. course I will have no way to apply this to your field The fact that we don’t know, really do not know directly when I tell you about it. However, there are what we’re doing, and the fact that the built world is undoubtedly abundant connections between the not nurturing is a very, very drastic matter for all of two fields that can be drawn. us. This is my concern. That is what I try to deal with 3. What the Future Holds in Store: The Gener- every day. ativity Problem and the Generation of a Living World. At the time I wrote the introduction for Richard Gabriel’s book, that was really as far as I had PATTERN THEORY gotten in trying to trace the connection between my work and your work in the field of computer sci- The idea that materialized in the published pattern ence: I tell you what I’m doing, and maybe some of language was first of all, of course, intended just to get you folks might find it interesting or be able to ex- a handle on some of the physical structures that make trapolate. But I couldn’t really find that sufficient to the environment nurturing for human beings. And, be satisfying. I felt that there is some more signifi- secondly, it was done in a way that would allow this to cant connection between your field and mine. Or at happen on a really large scale. And, what I mean by that least that there perhaps is. And that finally brought is that we wanted to generate the environment indi- me to the third point. rectly, just as biological organisms are generated, indi- The third thing I’ll talk about is how I now per- rectly, by a genetic code. Architects themselves build ceive that connection. I suppose that some of you a very, very small part of the world. Most of the physi- know what I do for a living. You know I’m an archi- cal world is built by just all kinds of people. It is built by

September/October 1999 IEEE Software 73 developers, it is built by do-it-yourselvers in Latin the aim of creating coherence, morphological co- America. It is built by hotel chains, by railroad compa- herence in the things which are made with it. And nies, etc., etc. How could one possibly get a hold of all third, it is generative: it allows people to create co- the massive amount of construction that is taking place herence, morally sound objects, and encourages on Earth and, somehow, make it well, that means let it and enables this process because of its emphasis on be generated in a good fashion and a living fashion? the coherence of the created whole. This decision to use a genetic approach was not only I don’t know whether these features of pattern because of the scale problem. It was important from language have yet been translated into your disci- the beginning, because one of the characteristics of pline. Take the moral component, for example. In any good environment is that every the architectural pattern language there is, at root, part of it is extremely highly adapted behind the whole thing, a constant preoccupation to its particularities. That local adap- with the question, Under what circumstances is the tation can happen successfully only environment good? In architecture that means if people (who are locally knowl- something. It means something important and vital edgeable) do it for themselves. In tra- that goes, ultimately, to the nature of human life. Of ditional society where lay people ei- course, there are plenty of people who will debate ther built or laid out their own whether the question is objective. Some architects houses, their own streets, and so on, are still going around saying that it is all a matter of the adaptation was natural. It oc- opinion. But that is a dying breed. The moral preoc- curred successfully because it was in cupation with the need for a good environment, and the hands of the people that were di- for the living structure of built environment, and the rectly using the buildings and streets. objective nature of that question, is largely accepted. So, with the help of the shared pat- I do not know whether that sort of moral compo- Christopher Alexander tern languages which existed in tra- nent exists in computer science, or in software en- ditional society, people were able to gineering, or in the way in which you do things. generate a complete living structure. I understand that the software patterns, insofar In our own time, the production of environment as they refer to objects and programs and so on, can has gone out of the hands of people who use the make a program better. That isn’t the same thing, environment. So, one of the efforts of the pattern because in that sentence ‘better’could mean merely language was not merely to try and identify struc- technically efficient, not actually ‘good.’Again, if I’m tural features which would make the environment translating from my experience, I would ask that the positive or nurturing, but also to do it in a fashion use of pattern language in software has the ten- which could be in everybody’s hands, so that the dency to make the program or the thing that is whole thing would effectively then generate itself. being created morally profound—actually has the What, now, of my evaluation of what you are doing capacity to play a more significant role in human life. with patterns in computer science? (Bear in mind, as A deeper role in human life. Will it actually make you hear my comments, that they need to be taken human life better as a result of its injection into a with a grain of salt; I’m ignorant; I’m not in your field.) software system? Now, I don’t pretend that all the When I look at the object-oriented work on patterns patterns that my colleagues and I wrote down in A that I’ve seen, I see the format of a pattern (context, Pattern Language are like that. Some of them are pro- problem, solution, and so forth). It is a nice and use- found, and some of them are less so. But, at least it ful format. It allows you to write down good ideas was the constant attempt behind our work. That is about software design in a way that can be discussed, what we were after. I don’t know whether you, ladies shared, modified, and so forth. So, it is a really useful and gentlemen, the members of the software com- vehicle of communication. And, I think that insofar as munity, are also after that. I have no idea. I haven’t patterns have become useful tools in the design of heard a whole lot about that. So, I have no idea software, it helps the task of programming in that whether the search for something that helps human way. It is a nice, neat format and that is fine. life is a formal part of what you are searching for. Or However, that is not all that pattern languages are you primarily searching for—what should I call are supposed to do. The pattern language that we it—good technical performance? This seems to me began creating in the 1970s had other essential fea- a very, very vital issue. tures. First, it has a moral component. Second, it has People have asked me what kind of a process

74 IEEE Software September/October 1999 was involved in creating the architectural pattern concept, for you, is an inspiring format that is a good language. One of the things we looked for was a way of exchanging fragmentary, atomic ideas about profound impact on human life. We were able to programming. Indeed, as I understand it, that part judge patterns, and tried to judge them, according is working very well. But these other two dimen- to the extent that when present in the environment sions, (1) the moral capacity to produce a living we were confident that they really do make people structure and (2) the generativity of the thing, its ca- more whole in themselves. Of course you may ask, pability of producing coherent wholes—I haven’t How in the hell did you test for that? But that is too seen very much evidence of those two things in long a story which I cannot cover in this speech. The software pattern theory. Are these your shortcom- important point is that such testing was going on ings? Or is it just because I don’t know how to read continuously. A second, almost more important the literature? thing was going on. Whenever we had a language So much for my short historical survey of what under development we always asked ourselves, To we have been doing with pattern languages during what extent does that language generate (hence the last three decades. produce) entities (buildings, rooms, groups of build- ings, neighborhoods, etc.) that are whole and co- herent? In other words, suppose I write a pattern THE NATURE OF ORDER language for a campus, and, I think I’ve got some sort of a language that looks as though it will actu- The pattern theory was followed by a deeper the- ally do the job. To test it, I let it loose by giving it to ory. I began to notice, by the late ’70s, some weak- people and asking them (in simulated form) to gen- nesses in our work with patterns and the pattern erate different campuses with this language. Let’s languages. see what the resulting campuses look like. And we (1) Under the circumstances that I was most in- test it ourselves in the same way, by using it to gen- terested in, when we and others were using these erate designs, rapidly, and only for the purpose of patterns to generate buildings, the buildings gen- testing the results for their coherence. As it turns erated were okay but not profound. There was often out, many of the languages that one creates do not a lot of nice stuff going on in them. People were im- generate coherent designs or objects. That is, they proving certain features, perhaps the daylight was contain a bunch of good ideas. One can use these improved, or perhaps the entrance of a building was good ideas to (sort of ) put something together improved or the characteristics of a street might be from them, and a few fragmentary structural ideas improved or an alcove in a bedroom might make it will be present in the result. But that does not yet more intimate or something like this. So, there were mean that the campuses created (in the above ex- various isolated features of buildings that were im- ample) are coherent, well-formed, campuses. We provements in building performance. The existence were always looking for the capacity of a pattern of the patterns also allowed people to have better language to generate coherence, and that was the control over their own environment. It succeeded in most vital test used, again and again, during the embodying that control in the real buildings that process of creating a language. The language was they made with the pattern material. That was good. always seen as a whole. We were looking for the ex- But, nevertheless, were the buildings profound tent to which, as a whole, a pattern language would structures? To what extent did they really have co- produce a coherent entity. herent living structure as wholes? By the late ’70s, I Have you done that in software pattern theory? had begun to see many buildings that were being Have you asked whether a particular system of pat- made in the world when the patterns were applied. terns, taken as a system, will generate a coherent com- I was not happy with what I saw. It seemed to me puter program? If so, I have not yet heard about that. that we had fallen far short of the mark that I had But, the point is, that is what we were looking for all intended. But, I also realized that whatever was the time. Again, I have no idea to what extent that is going wrong wasn’t going to be corrected by writing true for you and whether you are looking for the a few more patterns or making the patterns a little same thing when you work on software patterns. bit better. There seemed to be something more fun- So far, as a lay person trying to read some of the damental that was missing from the pattern lan- works that have been published by you in this field, guage. So, I started looking for what that thing was. it looks to me more as though mainly the pattern (2) At about the same time I began to notice a

September/October 1999 IEEE Software 75 deeper level of structure and a small number (15) of truth; that is because everyone wants to do their own geometric properties that appeared to exist recur- stupid thing and get away with it. So, depending on sively in space whenever buildings had life. These 15 who you talk to, they’d say, ‘Well, this stuff Alexander’s properties seemed to define a more fundamental been discovering is a lot of nonsense. There is no such kind of stuff; similar to the patterns we had defined thing as objectivity about life or quality.’But, I am here earlier, but more condensed, more essential—some today, and they are not here, so I’m telling you that kind of stuff that all good patterns were made of. there is objectivity. They are simply mistaken. Let’s These were simple ideas. I can’t take you through suppose that we’ve got a sidewalk somewhere on a all 15 but they are properties like ‘boundaries’which bit of a street and we’ve got another sidewalk some- will not only delineate but connect the inside to the where else on another bit of a street. We are trying to outside, or ‘positive space,’ as when you look at a come to conclusions about which one has more life, Matisse cutout and see that the space between the which one is a more living structure. colored paper is not amorphous but also has form. My belief, by the way, when I began trying to find Anyway I began to notice that particular individual these experimental methods, always was that there patterns seemed really to come always from the 15 really is such a thing, and that actually everybody deep properties that kept occurring again and again. knows it, but that it has been suppressed. That is be- (3) Another thing that was happening around cause of the world view that we have and the way of this time (late ’70s, early ’80s), my colleagues and I looking at things and the nervousness about intel- began toughening up our ability to discriminate lectual rigor… that people of our era have. Although empirically between living structure and not living they have these judgments within them, somehow structure. During the years of doing the pattern lan- they are separated from their ability to make these guage, we’d really been intuitive about that and not judgments correctly. This is just some sort of child- very rigorous. We were just trying to get patterns ish instinct that everybody has and knows. But, for written and learning to apply them without asking some reason, we are so messed up that we can’t see rigorously if they made buildings with more life in it. So these experiments were, in effect, designed to them. But, at this point (about 1980), we felt it was penetrate that end result through. pretty important to get a fix on the difference be- The essence of the experiments is that you take tween a chair which has a more living structure and the two things you are trying to compare and ask, a chair that has a less living structure. And the same for each one, Is my wholeness increasing in the pres- for a building or a room or for a main street in a town. ence of this object? How about in the presence of If you want to say this one has life, this one has less this one? Is it increasing more or less? You might say life, how do you say that with any degree of empir- this is a strange question; What if the answer is ical certainty? Can it, in fact, be made a relatively ob- ‘Don’t know’or ‘They don’t have any effect on me’? jective matter which people can agree about if they Perfectly reasonable! That can happen. But the res- perform the same experiments? olution is easy. What turns out to happen is that if Indeed, we did find such experimental tech- you say to a person ‘Yes, it is a difficult question, it niques. The use of these techniques greatly sharp- might even sound a bit nutty. But anyway, please ened our ability to distinguish what was really going humor me and just answer the question.’ Then it on and what structures then correlated with the turns out that there is quite a striking statistical presence of life in a bit of the environment. The use agreement, 80–90%, very strong, as strong a level of of these techniques also helped us to refine the 15 agreement as one gets in any experiments in social deep geometric properties, as necessary correlates science. All of these different experiments have to of all life in designed structures. These 15 properties do with something like that. Do you feel more turned out to be a substrate of all patterns, and whole? Do you feel more alive in the presence of this began showing up more and more clearly in our thing? Do you feel that this one is more of a picture work as the main correlates of living structure in of your own true self than this thing you know what- places, buildings, things, space, and so forth. ever? It is always looking at two entities of some kind A brief side remark: I need to say a word about the and comparing them as to which one has more life. existence of objective criteria and experimental It appears to be a rank bit of subjectivity. In other methods. In my discipline there are tremendous words, it sounds like: ‘Well okay, fine; I mean maybe vested interests. Many architects claim, and want to this is the truth about human beings in the sense claim, that in architecture there is no such thing as about our coordination or about our perception or

76 IEEE Software September/October 1999 about our feelings.’ But that is not necessarily the an observer who looks at the code. same as saying living structure as such is a real thing The important thing is that—in architecture—this that resides in those objects. But anyway, to cut a is not merely a hunch but a testable empirical result. long story short, it turns out that these kind of mea- It means that the objects that are most profound surements do correlate with real structural features functionally (when I say objects, I mean buildings, in the thing and with the presence of life in the thing streets, door knobs, shelves, rooms, domes, bridges) measured by other methods, so that it isn’t just some are the ones which also promote the greatest feel- sort of subjective I-groove-to-this, and I-don’t- ing in us. This is a very peculiar thing. At first it sounds groove-to-that, and so on. But it is a way of measur- like rank sentimentality; and you just say, It can’t be ing a real deep condition in the particular things that true. Why should it be true? And yet, it’s a discovery are being compared or looked at. which accords very well with the era that we live in. What is odd about this, and in a way as our work Because we are living in a period where perhaps the went further and further, it kept bringing big func- most noticeable and most problematic feature of our tional and practical matters back to the human per- world is that feeling has been removed from it. When son. So, in other words, you take a parking lot. There I make a joke in reference to this horrible meeting are lots of technical problems in the parking lot. You hall that we are in, maybe I am beating a dead horse, have got to make it work. Cars have got to be able to but I mean really, the problem is that whatever feel- move around. You know there are security problems. ing there is in here is obviously not a profound pos- There are in-and-out problems. There are mainte- itive feeling. And this is what we have come to ex- nance problems. As a whole, the way a parking lot pect in our modern world. The failure of that works is essentially a technical thing. The question profound feeling to exist in the world around us at is, Is it working well or not well? And yet the func- small scales, large scales, middle scales, here, there, tionality of the thing measured by these various or- and everywhere, is tragic. It’s the thing that we miss. dinary bits of technical discussion correlates with the Of course, people have been writing about this for condition measured by the question, Do I feel my- many decades. Writers have, of course, made this self to be more whole? It works well when you are known. We all know it. The difficulty is that people getting a positive answer to this question. Thus don’t seem to know what to do about it. If anything, there is a hint of a profound connection between at the moment, (I’m talking now again about my own the nature of matter and behavior of material sys- discipline, of architecture) the problem is getting tems, and the human person. Even in engineering worse. It’s not getting better. The world that is being design, as for instance where one considers the built is more and more unfeeling. We are in a sense structural behavior of a bridge. Or the patterns of more lost, more fragmented, more sort of wander- movement in something where a lot of cars are mov- ing about in this lonely desert than before. ing about, and there are complicated questions If there really is a way of looking at structures about how they move and so forth. In these exam- which both deals with real functional structure in ples very, very practical matters are nevertheless cor- the ordinary technical and practical sense, and si- related with these apparently personal questions multaneously has its roots in human feeling, this will about whether the thing has life and whether it pro- be a very huge and positive step. In particular, the motes life in me and you. 15 properties that I have mentioned provide us the So there began developing, in my mind, a view ability to be precise about the nature of living struc- of structure which, at the same time that it is objec- ture, in just precisely such a way that it is connected, tive and is about the behavior of material systems not only to all mechanical function, but also to the in the world, is somehow at the same time coming depths of human feeling. That is why it is an impor- home more and more and more, all the time, into tant structure. the person. The life that is actually in the thing is cor- At the root of these 15 properties, there appears to related in some peculiar fashion with the condition be a recursive structure based on repeated appear- of wholeness in ourselves when we are in the pres- ances of a single type of entity—the primitive ele- ence of that thing. The comparable view, in software ment of all wholeness. These entities are what I call design, would tell you that a program which is ob- ‘centers.’All wholeness is built from centers, and cen- jectively profound (elegant, efficient, effective, and ters are recursively defined in terms of other centers. good as a program) would be the one which gen- Centers have life, or not, in different degree, according erates the most profound feeling of wholeness in to the degree that the centers are built from other

September/October 1999 IEEE Software 77 centers using the 15 geometric relationships which I that patterns are merely a few of the structural in- have identified. This scheme, which is at the founda- variants that appear within these centers under very, tion of all the work in The Nature of Order, provides a very particular conditions. So they’re certainly in- complete and coherent picture of all living structure. teresting and important, but they don’t have the Stretching a bit, I think there may even be a little bit same depth or the same universal character as these of a connection between the geometric centers which other structures that I’m speaking about now. appear as the building blocks of all life in buildings, Now we come to the crunch. Once we have the and the software entities that you call ‘objects.’Centers view of wholeness and centers, linked by the 15 are field-like structures that appear in some region of deep properties, we have a general view of the type of space. They don’t have sharp boundaries, but they are whole which must occur as the end product of any suc- the focal organizing entities that one perceives at the cessful design process. And because we have a view core of all pattern, all structure, and all wholeness. of it as a whole, we are now able to understand what Everything is made of these kinds of centers. The kinds of overall process can generate good struc- centers are more living or less living. And, that’s es- ture, and which cannot. This is the most significant sentially the only important property that they have. aspect of The Nature of Order, and of the new results And the question of whether a center is more living I am presenting to you in this Part 2. or less living depends recursively on the amount of It means that we can characterize not merely the livingness in the other centers that it is made of, be- structure of things which are well-designed, but we cause each living center is always (and can only be can characterize the path that is capable of leading defined as) a structure of other centers. This sort of to a good structure. In effect, we can specify the dif- recursion is familiar in computer science. But whether ference between a good path and a bad path, or be- the structure I have discovered and reported in The tween a good process and a bad process. Nature of Order will translate in any interesting ways In terms of software, what this means is that it is to things that you do, I don’t know. (It is true, I sup- possible, in principle, to say what kind of step-by- pose that all software is made of objects, and noth- step process can produce good code, and which ing but objects. Could it be said that some objects ones cannot. Or, more dramatically stated, we can, have more life, and others less? If so, there would be in principle, specify a type of process which will al- a profound correspondence). What is true, I can tell ways generate good code. you from my own experiences in these last years, is Of course we have not actually done this for the that when one has this view of things in architecture, production of code. We have done it for design and it becomes enormously easier to produce living construction of buildings. But it is possible. This is, if structure in buildings. It has immediate practical use- you like, the holy grail of software design—specifi- fulness. If you start understanding everything in cation of the kinds of process which will (always) terms of these living centers, and you recognize the generate good, efficient, economical, beautiful, and recursion that makes a center, living as it is, depen- profound, code. dent on the other centers that it is made of and the What are the details? I can tell you in the case of other larger centers in which it is embedded, sud- buildings. If one has identified living structure with denly you begin to get a view of things which almost a reasonable level of objectivity, and if one has iden- by itself starts leading you towards the production tified this recursive center-based structure as being of more successful and more living buildings. the key to the whole thing, that’s all very well. But This insight goes far beyond the power of the then of course the practical question arises, How the pattern language. Although the patterns define re- hell do you produce this living structure? What do lations which might be regarded as specific in- you have to do to actually produce it? You can clum- stances of the recursive interaction of centers, the sily try to find your way towards it in a particular case. overall view of centers gives a more comprehensive But, in general, what are the rules of its production? and more powerful results. It directly affects your The answer is fascinating. It turns out that these liv- ability to make good architecture, in a way that pat- ing structures can only be produced by an unfolding tern language was not yet able to do by itself. This wholeness. That it, there is a condition in which you is a much more powerful and beautiful view than have space in a certain state. You operate on it what’s embedded in the pattern languages, be- through things that I have come to call ‘structure- cause when one has constructed this view… you preserving transformations,’maintaining the whole say, well, what is a pattern really? Then it turns out at each step, but gradually introducing differentia-

78 IEEE Software September/October 1999 tions one after the other. And if these transforma- introducing this unfolding process and trying to tions are truly structure-preserving and structure-en- make it work under the conditions available to us in hancing, then you will come out at the end with liv- 1996. The social and technical shifts involved are ing structure. Just think of an acorn becoming an oak. large. The shifts in thought, in practice, in adminis- The end result is very different from the start point tration of money, in contracts, all sorts of real nitty- but happens in a smooth unfolding way in which gritty things that one would much rather not mess each step clearly emanates from the previous one. with because they are so hard, you must mess with Very abstract, I know, but the punchline is the fol- because it is those processes which are undermining lowing. That is what happens in all the living struc- the ability for our whole contemporary social tures we think of as nature. When you analyze care- process to be structure-preserving unfolding. If life fully just what’s going on and how things are is to be created, these processes must change. happening in the natural world, this sort of structure- That is the end of my Part 2. preserving transformation tends to be what’s going on most of the time. That is why, when nature is left alone, most of the time living structure is produced. WHAT THE FUTURE HOLDS IN STORE: However, in the approaches that we currently have to THE GENERATIVITY PROBLEM AND THE the creation of the built world and the environment GENERATION OF A LIVING WORLD (planning design, construction, and so forth), that is simply not what is happening. The process of design Let us now consider a problem of magnitude. that we currently recognize as normal is one where There are some two billion buildings in the world, the architect or somebody else is sort of moving stuff about 2 x 109 buildings. Differently stated, the total around, trying to get into some kind of good con- amount of built stuff is something on the order of figuration. Effectively this means searching in an al- about 1012, 1013 square feet of construction. The most random way in configuration space, and never total amount of built stuff in Manhattan is some- homing in on the good structure. That is why the pre- where on the order of 109 square feet. If you include sent-day structure of cities, buildings, conventional all the exterior space in the world as well, the part halls, and houses are so often lifeless. The processes of the outdoors that is somehow having to do with by which they are generated are—in principle—not human beings and is part of our immediate world— life creating or life seeking. gardens and streets and agriculture and all of that, If a process doesn’t go in the structure-preserving in the world—we’re somewhere up around 1014 way that I’m talking about, the result is never living square feet of constructed, designed space. structure. How are we going to deal with all that? How do In effect you can write theorems which say, Under we create, or generate, living order in 1014 square the kind of conditions which occur in the construc- feet of construction? What process could possibly tion industry today, you cannot produce living struc- accomplish this within, say, one generation—the ture. So, the poor folks who designed and built this next 25 years? The effort of architects, no matter convention center were stuck with something life- how hard we try and no matter how much good will less, because they were embedded in the wrong we put in, does not begin to scratch the surface of kind of process. There was nothing they could do that task. All the architects in the world, together, about it. It was part of the process by which this kind working as they do today, cannot design more than of entity is produced in today’s society. As things say 1010 square feet per year—a tiny, tiny percent- stand, it cannot come out with a living structure at age of what is needed—far too small to be effective. the end. That is a shattering discovery. I have, for many years, thought that this could A very large part of my work and that of my col- only be solved by a genetic approach—an approach leagues in the last years has been one of trying to where deep structure, spread through society, cre- define social processes, economic processes, ad- ates and generates the right sort of structure, very ministrative and management processes which are much as genetic code creates and generates or- of such a nature that they permit true structure- ganisms and ecological systems—indirectly, by let- preserving unfolding to occur in society, thus to ting loose life-creating process. allow the generation and production of living struc- That is what I still believe. But, today, I am con- ture. This is what I do most of the time: I’m trying vinced that the equivalent of the genes that act in or- to do real projects of one sort or another where I’m ganisms will have to be—or at least can be—software

September/October 1999 IEEE Software 79 packages, acting in society. If these software pack- to work. No problem. The patterns are self-evident ages are life creating, and accepted, and widely and true. They will spread. And, as a result, the world enough spread throughout the world, there is a of buildings will get better. Hey presto. chance we might get a grip on this problem: pro- But it hasn’t yet worked out like that. In practical vided that the software is freeing, liberating, allows terms, so far, I’ve done almost nothing. The pattern lan- each person individual control and decision mak- guage, how much has it influenced the environment ing power to do the right thing, and to create living of the world? A few thousand buildings have been in- structure, locally, wherever they are. This task must fluenced. There are a few people that have lived a few fall, inevitably, at least in part, on your shoulders. things and been influenced. But, meanwhile, we’ve still The people who were kind enough to invite me got this gigantic amount of construction out there to give this speech originally assured me that if I just which is defining the world that all of us live in that is still explained the intellectual history (as I have done so going on in exactly the same fashion. I believe that the far), there will be those among you who may find it cultural process of influence is simply too slow to be interesting, that somehow they might latch on to it able to take care of this problem. In other words, the or know how to translate it into something that’s process by which one discusses these kinds of things, more directly relevant to your own concerns. That is, shares ideas about them, gradually influences the way after all, just what you have done in the last five years people are thinking so that gradually larger and larger with pattern languages. There clearly is a useful par- percentages of bits of the environment might turn into allelism between our two disciplines. living structure. That is a very slow process, and I don’t However, after receiving this invitation, and con- think it is fast enough to do the job. And yet, as an ar- templating the questions I could raise, I started chitect, I view myself as responsible for that. Not of dwelling on a conviction that was growing in me. course, alone, but as a professional, my job is to try to This conviction led me to feel that there was a deeper understand how we can get hold of that—the entire coincidence in what you are doing in software de- structure of built environment, all over Earth—and do sign and what I am doing in architectural design. I something about it to make it better. began to feel that there is a deeper connection, For several years I have been asking myself how which suggests that the two disciplines might merge this effort can be expanded, and strengthened. It in a way that would benefit us both—you in your dis- must be our aim to make the world’s environment a cipline and me in my discipline. In the next few min- living structure, within one or two generations. How, utes I will try to sketch the nature of this connection. realistically, can that be done? As an architect, of course like anybody concerned So, today, I am standing before you, thinking to with these things, I have a passion to try and make myself: Right, I’m now talking to people who are in a these things happen. It’s not enough just to say, well, way the core of the computer revolution. You proba- living structure isn’t being produced. There is a ques- bly realize, I know you must realize the extent to which tion I must ask myself, a question I do ask myself, the world is gradually now being shaped more and which all the time is: Okay, well, what are we going to more and more, indirectly, by the efforts of all of you do about it? Here we’ve got this poor Earth sinking who are sitting in this room—because it is you who under the weight of all this dross. And, what are we control the function of computers and their programs. actually going to do? I do a $10 million project here It is the programs that control the shape of manu- and I do a $10 million project there. But that accom- facturing, the shape of the transportation industries, plishes virtually nothing. Life is short. A few of those construction management, diagnosis in medicine, projects…and what is it? It is an atom in the prover- printing and publishing. You almost can’t name a facet bial bucket. It’s nothing. All of the efforts of the ar- of the world which is not already, to some very strong chitectural brethren, even if I can persuade them of degree, under the influence of the programs that are the truth of these things, is still a drop in the bucket. being written to manage and control those entities That by itself, will not affect more than a thousandth or those operations. And this is still in its infancy. How part, perhaps no more than a millionth part, of the long has this been really going on? Not long. About structure covering the built part of the Earth. 10 or 15 years, though of course, the preparation for When I started out 25, 30 years ago, I really it goes a lot further back than that. But really this is thought that I would be able to influence the world quite new. It is going to look a whole lot different, very fast. Especially when I got to the pattern lan- even more powerful in its degree of influence. guage. I thought, boy, I’ve really done it. This is going And yet, as a professional body, I don’t think that

80 IEEE Software September/October 1999 you are yet fully aware of it. I’m probably speaking erative scheme is carried out, the results are always out of turn here but, you know, I’ve thumbed through different, because the generative scheme always the proceedings of this conference, for instance. Jim generates structure that starts with the existing con- was kind enough to show it to me yesterday. I don’t text, and creates things which relate directly and really see discussion about what, collectively, com- specifically to that context. Thus the beautiful or- puter scientists are supposed to be doing with all ganic variety which was commonplace in traditional these programs. How are they supposed to help the society could exist because these generative Earth? And, yet, the capacity to do that is sitting right schemes were used by thousands of different peo- here in this room. That is an amazing situation. You ple, and allowed people to create houses, or rooms, have so much power.... but that means that you also or windows, unique to their circumstances. have an enormous responsibility. When I first hit on the idea of creating, and using, Is there a chance you might take on the responsi- pattern languages, I was inspired by these tradi- bility for influencing, shaping, and changing the en- tional generative schemes, and thought that I was vironment? Interestingly, I think many of you do also essentially copying them. However, in the huge ef- have the inclination. When I had the pleasure of be- fort of creating a believable, new pattern language, ginning to meet some of the various folks who in- in the 1960’s the effort went entirely onto the indi- troduced themselves to me over the last year and a vidual patterns (their formulation, verification, etc.), half from the software community, I began to be fas- and the idea that they were to be used sequentially, cinated by the number of them that were closet ar- one after the other, dropped into the background. chitects. Greg Bryant, who worked on the 486 chip, is In fact, both A Pattern Language and The Timeless really interested in ecology and is an editor of Rain, an Way of Building say that the pattern language is to be ecological magazine. Bill Joy is writing about work- used sequentially. In practice, however, this feature stations in the concrete physical sense that is famil- dropped out of site, and was not emphasized in use. iar as an architect. John Gage, chief scientific officer As a result, the beautiful efficacy of traditional lan- of Sun, is interested in neighborhood schools, and guages and their simple and beautiful sequential in the process by which people can repair their own nature disappeared from view. physical neighborhoods by working together. Jim In our most recent work, that has changed. We Coplien is dealing with social structures in human are now focusing on pattern languages which are organizations. Mark Sewell from IBM wants to build truly generative. That means, they are sequences of houses. Dick Gabriel has, as his deepest passion, the instructions which allow a person to make a com- writing of poetry: another kind of art. I don’t have a plete, coherent building, by following the steps of long enough list. But my hunch is that an amazing the generative scheme. We have done this for number of you who got into this pattern game in the houses, for public buildings, for office furniture lay- pursuit of your normal professional endeavors are out, and so forth. It works. And it is powerful. also very profoundly interested in the real physical Compared to the pattern language that you’ve world, and its shape and its design, its deep feeling, seen in A Pattern Language, these generative its impact on human life. That is, the world in which schemes are much more like what you call code. we inhabit. It is therefore conceivable that you, col- They are generative processes which are defined by lectively, could change the very drastic situation of a sets of instructions that produce or generate de- destroyed environment that I described earlier. signs. They are, in fact, systems of instructions which Let me just go back to the structure-preserving allow unfolding to occur in space in just the way that unfolding process that I described in Part 2 of this I was talking about a minute ago (Part 2), and are talk. I talked about this structure-preserving un- therefore more capable of producing living struc- folding process. ture. The published pattern language by compari- When I first constructed the pattern language, it son is static. The new generative languages are dy- was based on certain generative schemes that exist namic and, like software, interact with context, to in traditional cultures. These generative schemes allow people to generate an infinite variety of pos- are sets of instructions which, carried out sequen- sible results—but, in this case, with a built-in guar- tially, will allow a person or a group of people to cre- antee of well-formed results. The design that is cre- ate a coherent artifact, beautifully and simply. The ated or generated is guaranteed, ahead of time, to number of steps vary: there may be as few as half a be coherent, useful, and to have living structure. dozen steps, or as many as 20 or 50. When the gen- You know the pattern language (the one for

September/October 1999 IEEE Software 81 architecture) consists of these objects which are in- to do it, because the methods they use are not ca- teresting and which you somehow try to put to- pable of it. For you it is different. The idea of genera- gether. But it’s possible to have processes or proce- tive process is natural to you. It forms the core of the dures which will go much further, actually generate computer science field. The methods that you have living structure. Because of the complexity of the at your fingertips and deal with everyday in the nor- situation in the world, and because of the way soft- mal course of software design are perfectly designed ware is going, software that is designed to do this to do this. So, if only you have the interest, you do could very rapidly take the world by storm. have the capacity and you do have the means. Why would computer scientists and software en- I heard a rumor at breakfast that some of the people gineers suddenly become responsible for the form and in this room have begun to worry about their jobs. I structure of the built environment? Is that not the have no idea if that is true. But I was told there is an un- province of architects, planners, agricultural experts, dercurrent of unease as to where all this—software de- forestry people, and civil engineers? It ought to be. But sign—is going. There is a huge expanding phenome- the members of these professions are not taking re- non of programming as an art, and yet an uneasiness sponsibility for the generative approach to living struc- about where it is all headed. What is it going to do? ture—and so cannot produce it. And, as far as I can see, My comment on this? Please forgive me, I’m they do not see it coming, and are not preparing them- going to be very direct and blunt for a horrible sec- selves to take it on, mentally or professionally. Therefore ond. It could be thought that the technical way in it will fall to someone else to do it instead. which you currently look at programming is almost In history, this kind of unexpected switch is a com- as if you were willing to be ‘guns for hire.’ In other mon thing. When a paradigm change occurs, in a dis- words, you are the technicians. You know how to cipline, it is not always the members of the old pro- make the programs work. ‘Tell us what to do, Daddy, fession who take it to the next stage. In the history of and we’ll do it.’That is the worm in the apple. the development in technical change, very often the What I am proposing here is something a little bit people responsible for a certain specialty are then fol- different from that. It is a view of programming as the lowed by a technical innovation. And then the people natural, genetic infrastructure of a living world which who become responsible for the field after the tech- you/we are capable of creating, managing, making nical innovation are a completely different group of available, and which could then have the result that people. When the automobile came along, the peo- a living structure in our towns, houses, work places, ple who built the buggies for the horse and buggy cities, becomes an attainable thing. That would be re- did not then turn into Henry Ford. Henry Ford knew markable. It would turn the world around, and make nothing about horse buggies. The people who were living structure the norm once again, throughout so- building automobiles came from left field, and then ciety, and make the world worth living in again. took over—and the horse and buggy died off. This is an extraordinary vision of the future, in It is conceivable to imagine a future in which this which computers play a fundamental role in mak- problem of generating the living structure in the ing the world—and above all the built structure of world is something that you—computer scientists— the world—alive, humane, ecologically profound, might explicitly recognize as part of your responsi- and with a deep living structure. I realize that you bility. Such a change, representing a kind of a level may be surprised by my conclusion. This is not what of marriage between you and me, is of an entirely I am, technically, supposed to have been talking different sort from the one that I was invited by Jim about to you. Or you may say, ‘Well, great idea, but Coplien to contemplate. I was brought here to an- we’re not interested.’I hope that is not your reaction. swer the question ‘Okay Chris, what new things have I hope that all of you, as members of a great profes- you been doing that might spin off and be useful to sion of the future, will decide to help me, and to help us in our neck of the woods?’Parts 1 and 2 of this talk yourselves, by taking part in this enormous world- were about that. But this Part 3 is about something wide effort. I do think you are capable of it. And I do quite different. I want you to help me. I want you to not think any other professional body has quite the realize that that problem of generating living struc- ability, or the natural opportunity for influence, to ture is not being handled well by architectural plan- do this job as it must be done. ners or developers or construction people now, and I’ve enjoyed talking to you very much. Thank you the Earth is suffering because of it. I believe there may for listening to me, and I would be most keen to lis- be no way that they are ever going to actually be able ten to your ideas on these topics.” ❖

82 IEEE Software September/October 1999