1. Component Based Software Engineering
Chris Sholar
11/4/2003
CS5667

2. Domain Engineering
Goal – “identify, construct, catalog and disseminate a set of software components that have applicability to existing and future software in a particular application domain.”
Additional – “establish mechanisms that enable software engineers to share these components – to reuse them – during work on existing and new systems.”

3. Domain Engineering Three major activities Analysis Construction
Dissemination: to scatter abroad, to spread widely.

4. The Analysis Process Five Steps Define the domain to be investigated
Categorize items extracted
Collect a representative sample of applications in the domain
Analyze each sample
Develop an analysis model for the objects

5. The book claims that domain analysis can be applied to any software engineering methodology and may be applied to conventional and object oriented development.
This is similar to noun extraction for identifying objects and creation of models for representation of the system.

6. Point Two Expanded Eight extra steps added… Select specific functions
Abstract functions
Define taxonomy or classification system
Identify common features
Identify specific relationships
Abstract the relationships
Derive a functional model
Define a domain language

7. Does this really help?
These steps provide a useful model for domain analysis, but do they help with deciding which components are appropriate for reuse?

8. Sample questions to ask
How common is the component’s function within the domain?
Is the component hardware dependent?
Does the hardware remain unchanged between implementations?
Is the design optimized enough for the next iteration?
Is reuse through modification feasible?
Can a nonreusable component be decomposed to produce reusable components?

9. Further Help Characterization process
Define some generic characterizations for the component.
e.g.
Importance of safety/reliability
Programming language
Concurrency in processing
These characteristics are shared by all software within a domain.
Establish a relevancy scale for the characteristics

10. Structural Modeling Includes Structure Points
Basis for component selection and categorization
Software can be characterized by structural models, so components can be categorized by structure points, architectural patterns.
Aircraft avionics has a structural model of architectural style.

11. Component Based Development
Occurs in parallel with domain engineering
Software team refines an architectural style that is appropriate for analysis model.
The architecture for the system is composed of components that are available from reuse libraries, or engineered to meet the custom needs.

12. Three Phases Component Qualification
Ensures that a candidate component will perform the function required, and has the quality characteristics required.
Factors considered
API
Development and integration tools required
Runtime requirements
Security features
And others

13. Component Adaptation
Ideally domain engineering produces libraries of components that are easily integrated.
Implications
Consistent resource management
Data management exists for all components
Interfaces within architecture and with external environment are consistent

14. To remove some of the conflicts the previous implications produce, component wrapping is used.
When source code is available, often not with COTS, white box wrapping is used.
Code-level changes to fix conflicts
When the component library provides component extension languages or APIs that allow the conflicts to be masked or removed, this is called gray box wrapping.
Black box wrapping requires the use of pre- and post-processing at the component interface.

15. Component Composition
Assembles qualified, adapted, and engineered components to fill the architecture with the needed functionality.
Four architectural ingredients needed to create a coherent software package from components:
Data exchange model
Automation
Structured storage
Underlying object model

16. Underlying object model
Data exchange model
Enables users and applications to interact and transfer data
Automation
Tools, macros, scripts implemented to provide for interaction between components
Structured storage
Heterogeneous data should be organized and accessed as a single data structure
Underlying object model
Ensures that components of different programming languages and built on different platforms can be interoperable.

17. Summary
Domain engineering and component based development occur simultaneously in the CBSE process.
Domain engineering creates software components for reuse
Component based development refines the components chosen for the system.
Economics…