Software design pattern
In software engineering, a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into source or machine code. It is a description or template for how to solve a problem that can be used in many different situations. Patterns are formalized best practices that the programmer must implement themselves in the application. Object-oriented design patterns typically show relationships and interactions between classes or objects, without specifying the final application classes or objects that are involved. Many patterns imply object-orientation or more generally mutable state, and so may not be as applicable in functional programming languages, in which data is immutable or treated as such. Design patterns reside in the domain of modules and interconnections. At a higher level there are architectural patterns that are larger in scope, usually describing an overall pattern followed by an entire system. There are many types of design patterns, for instance
* Algorithm strategy patterns addressing concerns related to high-level strategies describing how to exploit application characteristics on a computing platform. * Computational design patterns addressing concerns related to key computation identification. * Execution patterns that address concerns related to supporting application execution, including strategies in executing streams of tasks and building blocks to support task synchronization. * Implementation strategy patterns addressing concerns related to implementing source code to support 1. program organization, and
2. the common data structures specific to parallel programming. * Structural design patterns addressing concerns related to high-level structures of applications being developed. -------------------------------------------------
Patterns originated as an architectural concept by Christopher Alexander (1977/79). In 1987, Kent Beck and Ward Cunningham began experimenting with the idea of applying patterns to programming and presented their results at theOOPSLA conference that year. In the following years, Beck, Cunningham and others followed up on this work. Design patterns gained popularity in computer science after the book Design Patterns: Elements of Reusable Object-Oriented Software was published in 1994 by the so-called "Gang of Four" (Gamma et al.), which is frequently abbreviated as "GOF". Although design patterns have been applied practically for a long time, formalization of the concept of design patterns languished for several years. In 2009 over 30 contributors collaborated with Thomas Erl on his book, SOA Design Patterns. The goal of this book was to establish a de facto catalog of design patterns for SOA and service-orientation. (Over 200+ IT professionals participated world-wide in reviewing Erl's book and patterns.) These patterns are also published and discussed on the community research site soapatterns.org -------------------------------------------------
Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems, and it also improves code readability for coders and architects who are familiar with the patterns. In order to achieve flexibility, design patterns usually introduce additional levels of indirection, which in some cases may complicate the resulting designs and hurt application performance. By definition, a pattern must be programmed anew into each application that uses it. Since some authors see this as a step backward from software reuse as...