Almost every ‘system as a whole’ is generated by a ‘generating system’. If we wish to make things which function as ‘wholes’ we shall have to invent generating systems to create them.
> pattern languages contain an inherent rule set that determines their logic
In an interview with his biographer, Alexander noted, *“We give names to things but we don’t give many names to relationships”*
> systems may come to necessitate their own propagation … when we use them
“Next, several acts of building, each one done to repair and magnify the product of the previous acts, will slowly generate a larger and more complex whole than any single act can generate”
… the architectural equivalent of the semantic networks: the interrelations of the words, their meanings and their evocations with each other.
… the language provides the framework for using the patterns as a program to create form. But he aims for semantics, allegory, and poetics, as well as the aspects of language that generate feelings, emotions, a sense of order — all of which extend beyond the structural, topological and syntactic aspects of his program.
In order to develop a model for stability in design problems, Alexander looked to cybernetics for models of homeostasis and ultrastability. Such systems could stabilize themselves regardless of what disturbed them, including variables that weren’t considered when the system was designed.
Ultrastability places two sets of environmental and reactive variables in a primary feedback loop. A slower, second feedback affects the reactive variables by acting on the step-mechanisms and setting parameters for the environmental variables.
His theory is based on a fundamental critique on classic physics and its deductive methods and focus on isolated phenomena. Bertalanffy considered such methods as unsuitable for biology,
> complex systems of interactions and reciprocities
… an overall design problem cannot be divided into sub-problems, and consequently, that it is impossible to arrive at a novel design solution as a summary process of solving individual problems one after the other.
The system behaviour emerges only in the dynamics of the interactions of the parts. This is not a cumulative linear effect but rather a cyclical causal effect.
This shift in architectural thinking introduced fundamental concepts for how the computation of such interrelational, complex behaviour-based systems could be achieved.
Design forms through the iterative readings and responses to interrelational conditions, with the intention of producing environments synchronous with their cultural settings.
How such a system is born, itself, of a generative system, establishing the duality between the object as a computing agent and the method as a computational process.
> emergence is a property of a whole that is not a property in its parts
Generative patterns work indirectly; they work on the underlying structure of a problem (which may not be manifest in the problem) rather than attacking the problem directly. Good design patterns are like that: they encode the deep structure (in the Senge sense) of a solution and its associated forces, rather than cataloging a solution.
> we often attack only symptoms, leaving the underlying problem unresolved
The structures of a pattern are not themselves solutions, but they generate solutions.
> a means of letting the problem resolve itself over time, just as a flower unfolds from its seed
Thus, as in the case of natural languages, the pattern language is generative. It not only tells us the rules of arrangement, but shows us how to construct arrangements as many as we want which satisfy the rules.
> Lao Tsu principles of nonaction
What, exactly, does it mean to say that structures generate particular patterns of behavior?
… a fundamental characteristic of complex human systems … [is that] cause and effect are not close in time and space. By effects, I mean the obvious symptoms that indicate that there are problems drug abuse, unemployment, starving children, falling orders, and sagging profits. By cause I mean the interaction of the underlying system that is most responsible for generating the symptoms, and which, if recognized, could lead to changes producing lasting improvement. Why is this a problem? Because most of us assume they are most of us assume, most of the time, that cause and effect are close in time and space.
> we need to address most interesting problems with emergent behavior
The pattern form excels an engaging the reader in generative solutions: to understand the principles and values of lasting solutions and long-term emergent behavior. Good patterns go beyond the quick fix.
Holistic behaviour is that instability which occurs in objects that are very vulnerable to a change in one part: when one part changes, the other parts change also.
*The most important properties which anything can have are those properties that deal with its stability.*
Stability, no matter in which of its many forms, is a holistic property. It can only be understood as a product of interaction among parts.
In order to speak of something as a system, we must be able to state clearly: (1) the holistic behaviour which we are focusing on; (2) the parts within the thing, and the interactions among these parts, which cause the holistic behaviour we have defined; (3) the way in which this interaction, among these parts, causes the holistic behaviour defined. If we can do these three, it means we have an abstract working model of the holistic behaviour in the thing. In this case, we may properly call the thing a system, If we cannot do these three, we have no model, and it is meaningless to call the thing a system. … We must not use the word system, then, to refer to an object. A system is an abstraction. It is not a special kind of thing, but a special way of looking at a thing.
The formal systems of mathematics are systems in this sense. The parts numbers, variables, and signs like + and =. The rules specify ways of combining three parts to form expressions, and ways of forming expressions from other expressions, and ways of forming true sentences from expressions, and ways of forming true sentences from other true sentences. The combinations of parts, generated by such a system, are the true sentences, hence theorems, of mathematics. Any combination of parts which is not formed according to the rules is either meaningless or false.
A generating system, in this sense, may have a very simple kit of parts, and very simple rules.
Alexander doesn’t rule out spontaneous order, but sees that as a rare event. For a system as a whole to have the properties desired, the builders will most probably have to have a generating system to create the system as a whole.
> processes which then maintain the system’s equilibrium
Most designers today think of themselves as the designers of objects. If we follow the argument presented here, we reach a very different conclusion. To make objects with complex holistic properties, it is necessary to invent generating systems which will generate objects with the required holistic properties.
Creating building systems in the present sense is not enough. We need a new, more subtle kind of building system.