Design Patterns Arose from Architecture and Anthropology

Years ago, an architect named Christopher Alexander asked himself, “Is quality objective?” Is beauty truly in the eye of the beholder or would people agree that some things are beautiful and some are not? Now, the particular form of beauty that Alexander was interested in was one of architectural quality: what makes us know when an architectural design is good? For example, if a person were going to design an entryway for a house, how would he or she know that the design was good? Can we know good design? Is there an objective basis for such a judgment? A basis for describing our common consensus?

Alexander postulates that there is such an objective basis within architectural systems. The judgment that a building is beautiful is not simply a matter of taste. We can describe beauty through an objective basis that can be measured.

The discipline of cultural anthropology discovered the same thing. That body of work suggests that within a culture, individuals will agree to a large extent on what is considered to be a good design, what is beautiful. Cultures make judgments on good design that transcend individual beliefs. I believe that there are transcending patterns that serve as objective bases for judging design. A major branch of cultural anthropology looks for such patterns to describe the behaviors and values of a culture. ^[2]

^[2] The anthropologist Ruth Benedict is a pioneer in pattern-based analysis of cultures. For examples, see Benedict, R., The Chrysanthemum and the Sword, Boston: Houghton Mifflin, 1946.

The proposition behind design patterns is that the quality of software systems can also be measured objectively.

If you accept the idea that it is possible to recognize and describe a good quality design, then how do you go about creating one? I can imagine Alexander asking himself,

What is present in a good quality design that is not present in a poor quality design?

and

What is present in a poor quality design that is not present in a good quality design?

These questions spring from Alexander's belief that if quality in design is objective, then we should be able to identify what makes designs good and what makes designs bad.

Alexander studied this problem by making many observations of buildings, towns, streets, and virtually every other aspect of living spaces that human beings have built for themselves. He discovered that, for a particular architectural creation, good constructs had things in common with each other.

Architectural structures differ from each other, even if they are of the same type. Yet even though they are different, they can still be of high quality.

For example, two porches may appear structurally different and yet both may still be considered high quality. They might be solving different problems for different houses. One porch may be a transition from the walkway to the front door. Another porch might be a place for shade on a hot day. Or two porches might solve a common problem (transition) in different ways.

Alexander understood this. He knew that structures couldn't be separated from the problem they are trying to solve. Therefore, in his quest to identify and describe the consistency of quality in design, Alexander realized that he had to look at different structures that were designed to solve the same problem. For example, Figure 5-1 illustrates two solutions to the problem of demarking an entryway.

Alexander discovered that by narrowing his focus in this way—by looking at structures that solve similar problems—he could discern similarities between designs that were high quality. He called these similarities, patterns.

He defined a pattern as “a solution to a problem in a context.”

Each pattern describes a problem which occurs over and over again in our environment and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice.^[3]

^[3] Alexander, C., Ishikawa, S., Silverstein, M., A Pattern Language, New York: Oxford University Press, 1977, p. x.

Let's review some of Alexander's work to illustrate this. In Table 5-1 I will present an excerpt from his The Timeless Way of Building,^[4] an excellent book that presents the philosophy of patterns succinctly.

^[4] Alexander, C., Ishikawa, S., Silverstein, M., The Timeless Way of Building, New York: Oxford University Press, 1979.

Table 5-1. Excerpt from The Timeless Way of Building

Alexander Says …	My Comments …
In the same way, a courtyard, which is properly formed, helps people come to life in it.	A pattern always has a name and has a purpose. Here, the pattern's name is Courtyard and its purpose is to help people to come to life in it.
Consider the forces at work in a courtyard. Most fundamental of all, people seek some kind of private outdoor space, where they can sit under the sky, see the stars, enjoy the sun, perhaps plant flowers. This is obvious.	Although it might be obvious sometimes, it is important to state explicitly the problem being solved, which is the reason for having the pattern in the first place. This is what Alexander does here for Courtyard.
But there are more subtle forces too. For instance, when a courtyard is too tightly enclosed, has no view out, people feel uncomfortable, and tend to stay away … they need to see out into some larger and more distant space.	He points out a difficulty with the simplified solution and then gives us a way to solve the problem that he has just pointed out.
Or again, people are creatures of habit. If they pass in and out of the courtyard, every day, in the course of their normal lives, the courtyard becomes familiar, a natural place to go … and it is used.	Familiarity sometimes keeps us from seeing the obvious. The value of a pattern is that those with less experience can take advantage of what others have learned before them: both what must be included to have a good design, and what must be avoided to keep from a poor design.
But a courtyard with only one way in, a place you only go when you “want” to go there, is an unfamiliar place, tends to stay unused … people go more often to places which are familiar.
Or again, there is a certain abruptness about suddenly stepping out, from the inside, directly to the outside … it is subtle, but enough to inhibit you.
If there is a transitional space—a porch or a veranda, under cover, but open to the air—this is psychologically half way between indoors and outdoors, and makes it much easier, more simple, to take each of the smaller steps that brings you out into the courtyard …	He proposes a solution to a possibly overlooked challenge to building a great courtyard.
When a courtyard has a view out to a larger space, has crossing paths from different rooms, and has a veranda or a porch, these forces can resolve themselves. The view out makes it comfortable, the crossing paths help generate a sense of habit there, the porch makes it easier to go out more often … and gradually the courtyard becomes a pleasant customary place to be.	Alexander is telling us how to build a great courtyard … … and then tells us why it is great.

To review, Alexander says that a description of a pattern involves four items:

• The name of the pattern

• The purpose of the pattern, the problem it solves

• How we could accomplish this

• The constraints and forces we have to consider in order to accomplish it

Alexander postulated that patterns can solve virtually every architectural problem that one will encounter. He further postulated that patterns could be used together to solve complex architectural problems.

How patterns work together will be discussed later in this book. For now, I want to focus on his claim that patterns are useful to solve specialized problems.