A catalogue of general-purpose software design patterns

Software design patterns describe proven solutions to recurring software design problems. Knowledge of these patterns increases designers' abilities, leads to cleaner and more easily maintained software, speeds up implementation and test, and helps programmers document and communicate their designs. This paper catalogues over 100 general-purpose design patterns. The organizing principle of the catalogue is the use of patterns, i.e., the problems they solve. Other considerations, such as whether a pattern is behavioral or structural, how it is implemented, or whether it is high or low level, are secondary, because these aspects are less important for a designer looking for a solution to a design problem. The catalogue collects general-purpose patterns from a variety of sources. It includes older patterns such as Module and Layers as well as modern, object-oriented patterns such as Observer and Visitor.