Chapter 22. The Evidence for Design Patterns

—Walter Tichy

Design patterns are reusable solutions for design problems. They became popular in 1995 with a famous book by Erich Gamma et al. [Gamma et al. 1995]. Before design patterns were introduced, programmers had only a few general design principles to guide them when structuring software. These principles included the information hiding principle, which says to equip software modules with change-invariant interfaces. This principle assures that the insides of a module can be changed while keeping the interface the same, and therefore none of the software using the module needs to be updated. The principle was formulated by Parnas [Parnas 1972] in response to the observation that software changes frequently.