Extensibility

Extensibility is a software engineering and systems design principle where the implementation takes future growth into consideration. The term extensibility can also be seen as a systemic measure of the ability to extend a system and the level of effort required to implement the extension. Extensions can be through the addition of new functionality or through modification of existing functionality. The central theme is to provide for change – typically enhancements – while minimizing impact to existing system functions. An extensible system is one whose internal structure and data flow are minimally or not affected by new or modified functionality, for example recompiling or changing the original source code might be unnecessary when changing a system’s behavior, either by the creator or other programmers. Because software systems are long lived and will be modified for new features and added functionalities demanded by users, extensibility enables developers to expand or add to the software’s capabilities and facilitates systematic reuse. Some of its approaches include facilities for allowing users’ own program routines to be inserted and the abilities to define new data types as well as to define new formatting markup tags.

Extensible design in software engineering is to accept that not everything can be designed in advance. A light software framework which allows for changes is provided instead. Small commands are made to prevent from losing the element of extensibility, following the principle of separating work elements into comprehensible units, in order to avoid traditional software development issues including low cohesion and high coupling and allow for continued development. Embracing change is essential to the extensible design, in which additions will be continual. Each chunk of the system will be workable with any changes, and the idea of change through addition is the center of the whole system design. Extensible design supports frequent re-prioritization and allows functionality to be implemented in small steps upon request, which are the principles advocated by the Agile methodologies and iterative development. Extensibility imposes fewer and cleaner dependencies during development, as well as reduced coupling and more cohesive abstractions, plus well defined interfaces.

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