Issues in Component-Based Software Engineering

Virtual Machine Interface: Interface of a component must be designed as a virtual machine. A component must provide a complete, non-redundant (i.e., minimal) interface. The interface must also hide internals (i.e., implementation decisions) of the components so that di erent implementations can be made for the component. Postponement of Context Binding: In the design of components, we need to strive for the development of "context free" components focusing only on the core functionality. To the extent it is possible, binding with particular contextual parameters such as data type, storage size, implementation algorithms, communication methods, operating environment, etc. should be postponed until the component integration time when performance optimization is made. Design Reuse: For component-based software integration to happen, design (i.e., component development context) must be shared and reused among the potential users. That is, design reuse must happen before component reuse. An architectural design shows the allocation of functionality to components and, for a component integration, reuse of the underlying architecture based on which components were developed must occur. Hierarchically Layered Architecture: Architectures and code components must be designed for maximum exibility in composing components. Figure 2 includes a layered architecture model [4] which seperates application task-oriented components, which do controlling and activity coordination, from functional components, which do mostly computations. Implementation techniques that are commonly used in the domain are separated from the functional components as implementation techniques can change for the same functions. Data communication models (e.g., message queue, task synchronization) are also separated from the technologies that implement various communication models. This architecture model allows postponement of the binding of particular implementation techniques until the component integration time when performance considerations are made. 4 Non-technical Issues One of the most serious problems that impede CBSE is the cost involved in producing reusable components. The cost of producing reusable components is substantially higher than the cost of producing a single application without reuse consideration, as high as ve