Ques : Describe Component Based Development

Ans :

There are three stages in this process. These are:
 Qualification,
 Adaptation (also known as wrapping),
 Composition (all in the context of components).

Component qualification: examines reusable components. These are identified by characteristics in their interfaces, i.e., the services provided, and the means by which consumers access these services. This does not always provide the whole picture of whether a component will fit the requirements and the architectural style. This is a process of discovery by the Software Engineer. This ensures a candidate component will perform the function required, and whether it is compatible or adaptable to the architectural style of the system. The three important characteristics looked at are performance, reliability and usability.

Component Adaptation is required because very rarely will components integrate immediately with the system. Depending on the component type(e.g., COTS or inhouse), different strategies are used for adaptation (also known as wrapping). The most common approaches are:

White box wrapping: The implementation of the component is directly modified in order to resolve any incompatibilities. This is, obviously, only possible if the source code is available for a component, which is extremely
unlikely in the case of COTS.

 Grey box wrapping: This relies on the component library providing a component extension language or API that enables conflicts to be removed or masked.

Black box wrapping: This is the most common case, where access to source code is not available, and the only way the component can be adapted is by pre / post-processing at the interface level.

It is the job of the software engineer to determine whether the effort required to wrap a component adequately is justified, or whether it would be “cheaper” (from a software engineering perspective) to engineer a custom component which removes these conflicts. Also, once a component has been adapted it is necessary to check for compatibility for integration and to test for any unexpected behavior which has emerged due to the modifications made.

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