9.5 The Roots: Alexander on Patterns and Pattern Languages

For Alexander, patterns, like people, are not isolated, separate, and distinct. Their value comes from their connectedness. What is important to establish first are the connections that any one pattern has. Then, within a pattern, establish its value and generativity by showing how it connects and combines the elements of the solution in a way that provides opportunities for creative use. Finally, patterns are woven into an interconnected web a pattern language that the user can traverse in an endless variety of ways, depending on the needs of the particular situation.

The form of Alexandrian patterns is anecdotal and essay-like. Each starts with a picture, which is meant to represent an archetypal example. This is followed by a description of the context as an introduction. The description is intended to provide the first level of connectedness for the pattern by explaining how it helps to complete larger patterns that is, by identifying other patterns in the pattern language at a different higher scale that can work with the pattern at hand.

Two versions of the problem statement follow:

The first Alexander dubs the headline: a short statement of the essence of the problem in bold type.
The second version is an extended discussion that includes examples, indications of how it can be "manifested" and validated, and anything else that helps the reader situate the problem.

Finally, separated from the rest of the pattern by a highly visible "Therefore:" comes the solution: simple, terse, straightforward text and a sketch illustrating the solution to finish the pattern. Both the words and the pictures are necessary. They constitute what Donald Schon describes as "the language of designing:"

Drawing and talking are parallel ways of designing, and together make up what I call the language of designing. The verbal and non-verbal dimensions are closely connected. (Schon 1983, 41)

Because Alexander is an architect, his solutions are concerned with the built environment. His patterns are too long to quote in one piece, but a summary of a typical pattern provides at least some of the flavor of both their organization and their impact.

In one example, Alexander talks about the forces that have to be considered while solving the problem of building entrances. The general context is that a building is connected to public space. The context within the language is defined by other patterns dealing with Main Gates and Half-hidden Gardens.

The forces involved include the need for a "feeling of arrival," specifically, a psychological need to signal the possibility of more intimate behavior than the "street behavior" common to a public space. Coming in from the outside usually means bringing this psychological balloon of street behavior along, however.

Then, for a house (for example), there's also a need to feel that entering means entering a private domain. But the outside world is visibly public, so how is the change from public to private going to be made apparent and reinforced? (Both of these "forces" work in reverse as well; "leaving" is as much a part of the picture as arriving.)

Finally, there are technological forces to consider: at home (again as an example), most people these days arrive and leave via a car. But where and how a car is parked may be determined by convenience and add forces that are related to the convenience of the entrance with respect to the car's parking spot.

There are really three interrelated patterns here. Alexander's three solutions: create a visible and identifiable main entrance; have a varied, graduated and obvious transition area; and treat the connection to the car as a special form of transitional space. He calls these patterns Main Entrance, Entrance Transition, and Car Connection. His solutions are a great deal more detailed than my summary statement, and the descriptions of context and forces include examples and are not at all cut-and-dried. But all follow the same meta-pattern, regardless of level or topic. In software terms, his patterns are scaleable, as well as reusable and architected.

Of course, Alexander has a large number of patterns that are more bricks-and-mortar than this one. All of them emphasize what might be called social geometry, however: the relationship between how you organize what you build on the grid of the social dimensions that are the underlying needs to be met.

In the same way that words combined into phrases make speech possible as a creative act, patterns in combination are the basis for creative design and building. As in spoken language, a tacit structuring of the patterns as language elements in the pattern language and the possibility of dynamically arranging and rearranging them is what gives both patterns and the pattern language a generative and creative aspect.

For the patterns practitioner, the interconnectedness of the patterns makes possible results, which are themselves also connected and more than the simple sum of their parts. Alexander describes this as "compression": Putting Atogether with Bresults in a whole that is richer and healthier and better than the individual parts in isolation, and it is denser in "meaning" more than simple synergy. A quality emerges from the combination that is inexplicable solely in terms of the individual elements.

Alexander's pattern language is structured by scale. But his scale combines the physical and the social; it is not just about "numbers of houses." It is also about the events and interactions the life that take place in those houses, a life that both derives from and shapes the way they are arranged and built. So, his patterns include social context and comment in discussing the driving forces behind each solution.

For example, at the highest level, patterns about the size of regions and the physical interweaving of city and country are leavened by a pattern called Lace Of Country Streets, which includes the observation that "the suburb is an obsolete and contradictory form of human settlement" (Alexander, Ishikawa, and Silverstein 1977, 244). Another example is Scattered Workplaces, which talks about the need to avoid dead spaces where only work is accommodated: "Prohibit large concentrations of work, without family life around them."