Design pattern (architecture)

The idea of capturing design ideas as a "pattern" is usually attributed to Christopher Alexander, an architect. The patterns serve as an aid to design cities and buildings. The concept of having collections of "patterns" or typical samples as such is much older. One can think of these collections as forming a pattern language, whereas the elements of this language may be combined governed by a certain rules.

Alexander's patterns seek to provide a source of proven ideas for individuals and communities to use in constructing their living and working environment. As such their aim is both aesthetic and political: to show how beautiful, comfortable, flexible, built environments can be constructed, and to enable those people who will inhabit those environments to challenge any solution forced upon them.

Patterns are not invented, but discovered. (Taken to its logical conclusion, this would imply in the field of software that automated analysis tools must theoretically be able to be designed which "dig for" and "discover" patterns in large bodies of existing source code.) A pattern records the design decisions taken by many builders in many places over many years in order to resolve a particular problem. Alexander describes a problem in terms of the so-called forces that act in it, and the solution is said to resolve those forces.

Patterns may be collected together into a pattern language that addresses a particular domain. A large body of patterns was published by Alexander and his collaborators as A Pattern Language. The patterns in that book were intended to enable communities to construct and modify their own homes, workplaces, towns and cities.

Few building projects have tried to use Alexander's patterns. Those that have, have met a mixed responses from other architects and builders, architectural critics and even the users of the buildings.

While the idea has had limited impact in the building industry, it has had a profound influence on many workers in the information technology industry.