kitchens; efficiency apartment kitchens; …all industrial sites larger than two acres; a 2x4… residential areas with 40 percent of their population under 25 and median incomes between $6,000 and $8,000; garden paths; cobblestone paths; a doorknob; any freeway; freeway exit ramps; bookshelves [ 6].” Any of these patterns provides a solution to a problem that exists in space, whether the demographics of a neighborhood, the kind of structure required for a house, a transportation issue, or the optimal setup of a dormitory.

As an example, the Pattern Manual describes the difficulty of reading house numbers from a moving vehicle. It states the context tersely and specifically: “Freestanding house on a street where cars move at speeds between 5 miles per hour and 30 miles per hour [ 6].” The problem statement is much longer—in this case, three pages—and sets out the series of issues the pattern will need to address, beginning with: “House numbers are very hard to see from moving cars, especially for the driver. Many signs are parallel to the road (on the house face, or garden gate), so that they can’t be seen from up the street [ 6].” The rest of the problem statement includes facts about house numbers and signage, references to studies on driver vision, and the limits of potential positioning of signs—in essence, the evidence for a case to support the problem. The following pattern, for instance, addresses the house-number problem:

• Two house signs, each at about 45 degrees to the street, facing up and down the street, respectively.

• If the house is one of a regular sequence of houses all using this pattern, then the sign letters are at least 6 inches high.

• If the house is isolated, or is one of a regular sequence of houses not using this pattern, then the sign letters are at least 12 inches high [ 6].

Consequently, a simple pattern that addresses angle and direction of signage and the size of letters tackles a broader design problem. It notes different use cases—sequences of similar houses versus isolated or nonse-quenced houses—and offers different variables for the solutions. While a designer could simply use the pattern, the richness of the framework lies in the overall problem statement and context.

Furthermore, the goal of pattern libraries is not only to offer solutions to design problems, but also to solicit critique and invite improvement. “We want our ideas to improve under public scrutiny,” wrote Alexander’s team, “and we want our good ideas to be potentially combined with other good ideas [ 6].” The Center for Environmental Structure first sought to publish its patterns under the rubric of a catalog to which anyone could submit patterns using the format described in this article. An editorial board would select patterns; catalog subscribers would receive the patterns. Alexander and his colleagues thought that by 1970, patterns could be stored in a computer and offered to subscribers—a central feature to contemporary pattern libraries for games, object-oriented programming, or Web design [ 9].

Through their straightforward approach to describing a complex network of design consider-

ations, Alexander, Ishikawa, and Silverstein all anticipated and inspired contemporary methods for design thinking. By seeking to provide “a natural way of expressing thoughts about the physical environment,” the authors offered a vital means to articulate the richness not only of a design solution, but its problem and its context [ 6]. At the same time, the earlier publication of Pattern Manual serves as a reminder for elements of patterns that often receive less focus. At the heart of every pattern is a design problem. When well defined, the design problem represents the designer’s collective expertise of issues, information, and problem context, making for better patterns and design solutions. In examining how the pattern language developed, we see how important the latter parts of that sentence were to Alexander and his colleagues—and to the continued evolution of design thinking in general. With straightforward language, the problem and pattern language continue to bring a systematic approach to design to the wider audience who practiced it, improved upon its elements, and continue to develop the concept today.

[ 9] Alexander, C.
Theory, Organization,
Activities. [Pamphlet],
Berkeley, Center
for Environmental
Structure, 1968.

ABOUT THE

AUTHOR Molly Wright
Steenson is a design
researcher and architectur-
al historian who studies
interactivity and respon-
siveness in architecture and urbanism. She
is a Ph.D. candidate in architecture at
Princeton University and contributing editor
for interactions. Steenson also conducts
research and develops design strategy for
mobile, Web, and urban projects and blogs at
Active Social Plastic ( activesocialplastic.com).

March + April 2009

DOI: 10.1145/1487632.1487637
© 2009 ACM 1072-5220/09/0300 $5.00