Chapter 30

Chapter 30

Component-Based Software Engineering

CHAPTER OVERVIEW AND COMMENTS

This chapter describes component-based software engineering (CBSE) as a process that emphasizes the design and construction of systems with reusable software components. CBSE has two parallel engineering activities, domain engineering (discussed earlier in the text) and component-based software development. The important point to emphasize to students is that custom software components are only created when existing components cannot be modified for reuse in the system under development. It is also important to remind students that formal technical reviews and testing are still used to ensure the quality of the final product. The advantage, of course, is that less time is spent designing and coding, so software can be produced less expensively. Students would benefit from having access to a library of commercial off-the-shelf components or at least a locally developed component library.

30.1  Engineering of Component-Based Systems           

It is important to have students understand the differences between CBSE and object-oriented software engineering. The biggest difference is that in CBSE, after the architectural design is established, the software team examines the requirements to see which can be satisfied by reusing existing components rather than constructing everything from scratch. In object-oriented software engineering, developers begin detailed design immediately after establishing the architectural design. Students need to understand the software activities that take place once reusable components are identified (component qualification, component adaptation, component composition, and component update).  These activities will be described in more detail later in the chapter. It may be worthwhile for students to be given a set of requirements and an indexed collection of reusable components and try to determine which requirements can be satisfied by the reusable component and which cannot.

30.2  The CBSE Process

This is a short section that contains schematic diagrams (Figure 30.1) for the two CBSE engineering activities (domain engineering and component-based engineering). Be sure students understand the interrelationships between the domain engineering and component-based engineering activities. The activities are discussed in more detail in the subsequent chapter sections.

30.3  Domain Engineering

Students should make sure they understand the three major domain engineering activities (analysis, construction, and dissemination). It is important for students to remember is that the purpose of conducting domain analysis is to identify reusable software components. Structural modeling is an important pattern-based domain engineering approach. Students may benefit from trying to conduct their own domain analysis. Alternatively, they may benefit from discussing a real world case study that includes domain analysis.

A useful exercise is to have students identify domain classes (or functions) for a domain such as “retailing” or “health care.”

30.4  Component-Based Development

Component-based software development activities are discussed in detail in this section. If students have access to a library of reusable components (or COTS components) they should be encouraged to use the composition techniques presented to assemble a new software product. Students may benefit from using one of the free component libraries like JavaBeans. Another good exercise might be to have students try to design one of their own software components so that is can be added to an existing software reuse library.

30.5  Classifying and Retrieving Components

This section discusses the issues associated with indexing and retrieving software components from a reuse library.  It also describes the necessary features for a component reuse environment. The material is presented at a fairly general level. If your students are familiar with multimedia databases and client-server computing, you might explore some of the implementation concerns that need to be addressed to construct a reuse repository by examining a real life example of one.

27.6  Economics of CBSE

This section discusses the economics of software reuse by examining its impact on software quality, programmer productivity, and system development cost. The calculations are not hard to follow. Students might appreciate seeing the benefits gained from reuse by examining project data from a real world example. Some discussion of structure points during project estimation appears in this section. Students might appreciate seeing a complete example that uses structure points as part of the cost estimation process. Some reuse metrics are defined. Students might be encouraged to compute the reuse metrics for their own software projects.