Patterns and Pattern Languages - Architecture

Notes from the "Roy Fielding's Dissertation"

A design pattern is defined as an important and recurring system construct.

A pattern language is a system of patterns organized in a structure that guides the patterns’ application. Both concepts are based on the writings of Alexander et al. [3, 4] with regard to building architecture.

A pattern defines a process for solving a problem by following a path of design and implementation choices.

Alexander's design philosophy is to identify patterns of life that are common to the target culture and determine what architectural constraints are needed to differentiate a given space such that it enables the desired patterns to occur naturally. Such patterns exist at multiple levels of abstraction and at all scales.

An architectural style as a co-ordinated set of constraints is applied to design space in order to induce the architectural properties that are desired of the system. By applying a style an architect is differentiating the software design space in the hope that the result will better match the forces inherent in the application, thus leading to system behaviour that enhances the natural pattern rather than conflicting with it.

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Patterns and Pattern Languages as Heuristics for Architecture.

Heuristics are an important aspect of architecture, an important informative tool if implemented correctly. A pattern or a set of patterns can be used as a heuristic for software architecture.