A Pattern Language: Towns, Buildings, Construction is a 1977 book on architecture, urban design, and community livability. It was authored by Christopher Alexander, Sara Ishikawa and Murray Silverstein of the Center for Environmental Structure of Berkeley, California, with writing credits also to Max Jacobson, Ingrid Fiksdahl-King and Shlomo Angel. Decades after its publication, it is still one of the best-selling books on architecture. The book creates a new language, what the authors call a pattern language derived from timeless entities called patterns. As they write on page xxxv of the introduction, "All 253 patterns together form a language." Patterns describe a problem and then offer a solution. In doing so the authors intend to give ordinary people, not only professionals, a way to work with their neighbors to improve a town or neighborhood, design a house for themselves or work with colleagues to design an office, workshop, or public building such as a school. Structure Written in the 1970s at the University of California, Berkeley, A Pattern Language is structured as a network, where each pattern may have a statement referenced to another pattern by placing that pattern's number in brackets, for example: (12) means go to the Community of 7,000 pattern. In this way, it is structured as a hypertext. It includes 253 patterns, such as Community of 7000 (Pattern 12) given a treatment over several pages; page 71 states: "Individuals have no effective voice in any community of more than 5,000–10,000 persons." It is written as a set of problems and documented solutions. According to Alexander & team, the work originated from an observation The book uses words to describe patterns, supported by drawings, photographs, and charts. It describes exact methods for constructing practical, safe, and attractive designs at every scale, from entire regions, through cities, neighborhoods, gardens, buildings, rooms, built-in furniture, and fixtures down to the level of doorknobs. The patterns are regarded by the authors not as infallible, but as hypotheses: Some patterns focus on materials, noting some ancient systems, such as concrete, during adaption by modern technology, may become one of the best future materials: Other patterns focus on life experiences such as the Street Cafe (Pattern 88): Grouping these patterns, the authors say, they form a kind of language, each pattern forming a word or thought of a true language rather than a prescriptive way to design or solve a problem. As the authors