1. Component-Based Development Process
Chapter 5
Component-Based Development Process
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2. Overview Software Process Models Component-based Development
Component-Based Software Lifecycle
Summary
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3. Purpose
This chapter:
Describes the component-based software lifecycle.
Provides an overview of generic software engineering processes.
Motivates the need for specific processes when developing components and when building systems or applications from components
Describe these processes, reviewing their procedures.
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4. Software Process Models
Generic lifecycle activities
The Sequential Model
Evolutionary Development
Unified Process
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5. Generic lifecycle activities
Requirements analysis and system specification
System and software design
Implementation and unit testing
Integration, system verification and validation
Operation support and Maintenance
Disposal
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6. The Sequential Model Analysis Development Design Implementation
Integration
Test
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7. Evolutionary Development
Develop a system gradually in many repetitive stages:
Increasing the knowledge of the system requirements and system functionality in each stage
exposing the results to user comments.
This can be achieved by using:
The Iterative Model
The Incremental Model
The Prototyping Model
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8. The Iterative Model Analysis Development Design Implementation
Integration
Test
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9. The Incremental Model Increment 1 2...n Development Analysis Design
Implementation
Integration
Test
Development
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10. The Prototyping Model Test prototype Analysis Development Design
Implementation
Integration
Test
Development
Develop
prototype
Test prototype
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11. Unified Process Inception
The first phase in which the system is described in a formalized way, providing a base for further development.
Elaboration
The phase in which the system architecture is defined and created.
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12. Unified Process continued
Construction
The development of completely new products, with reuse capabilities.
Transition
The work of delivering the product to the customer.
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13. Unified Process Illustrated
Inception
Elaboration
Construction
Transition
Requirements
Analysis
Design
Implementation
Test
Iter #1
Iter #n
Iter #2
---
An iteration in the
elaboration phase
Phases
Iterations
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14. Component-based Development
Reuse Approach
Separation of Development Processes
Component-based Development (CBD) – The Consumer Perspective
Component Development (CD) – The Producer Perspective
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15. Reuse Approach The reuse approach makes the following assumptions:
All experience can be reused.
Reuse typically requires some modification of objects being reused.
Reuse must be integrated into the specific software development.
Analysis is necessary to determine when, and if, reuse is appropriate.
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16. Reuse
For given requirements r for an object x, we propose the reuse of the already existing object xk. The reuse procedure includes:
Identification of a set of objects x1 , x2 … xm as candidates,
Selection of one of these, and, if required,
Its modification to translate xk to x’ which is as close to x as possible.
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17. Reuse continued The object x can be of any type: A system architecture
An overall design
A design pattern
An infrastructure
Different types of components or services.
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18. Separation of Development Processes
Component development 
System development with components
Focuses on the identification of reusable entities and relations between them, beginning from the system requirements and from the availability of components already existing.
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19. Component Guidelines
Components are built to be used and reused in many applications and should thus be:
Well specified
Easy to understand
Sufficiently general
Easy to adapt
Easy to deliver and deploy
Easy to replace
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20. CBD – The Consumer Perspective
Typically a component consumer selects a component and then uses it in a software system.
The component lifecycle must be considered in relation to the lifecycle of the system as a whole.
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21. The Consumer Perspective Continued
Common considerations:
Will the component producer be able to deliver a new component version when this is required?
How will changes in a component in the system affect the behavior of another component?
Will the component be compatible with newer versions of the surrounding systems and applications?
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22. CD – The Producer Perspective
The producer of a component must take into consideration:
The business goal
Component functionality
Maintenance policy
The type of application and system in which the component will be used
The requirements of the system
The life expectancy of relevant systems
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23. Additional Considerations
The maintenance requirements of components and systems are not necessarily compatible.
The component’s maintenance requirements should be synchronous with those of the system in which they are to be incorporated.
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24. Disposal
Disposal of Component-based Systems generally takes place due to two different factors:
Dissatisfaction
Obsolescence
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25. Disposal: Dissatisfaction
Initiated by consumers when they conclude that:
The component no longer provides the support of the system it was intended to provide or;
That the system no longer needs the component.
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26. Disposal: Obsolescence
When a component becomes obsolete and the producer ceases component maintenance and operation support.
This is likely to occur when:
A new, more effective component with the same, similar or extended functionality is found.
The producer is not able to continue with support or maintenance.
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27. Disposal: Considerations
Both producer and consumer should arrive at a compromise with respect to the lifecycles of their different products.
The consumer should always have in mind an alternative solution, such as:
The replacement of the component with another developed internally or by another producers.
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28. Component-Based Software Lifecycle
Development With Components
Requirements Analysis and Definition
Component Selection and Evaluation
System Design
System Implementation
System Integration
Verification and Validation
System Operation Support and Maintenance
System Development Process
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29. Development With Components
Emphasis is placed on the reuse of pre-existing components, rather than on the implementation of the system designed.
First
Find reusable units which will meet the requirements specified and will be compliant with the system design.
Second
Determine the amount of extra effort required to use reusable units instead of units dedicated to a particular purpose.
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30. Requirements Analysis and Definition
The three analysis tasks:
Capture the system requirements and define the system boundaries.
Define the system architecture to permit component collaboration.
Define component requirements to permit the selection or development of the required components.
The approach is:
optimistic and an idealized view of the process.
It assumes that the component requirements can be precisely defined and that it is possible to find components
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31. Analysis and Definition Continued
Not finding a component which exactly satisfies the requirements necessitates the development of a new component.
The process of design and even requirements engineering will be combined with component selection and the evaluation process.
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32. Component Selection and Evaluation
The components selected must therefore be evaluated:
Technically
Non-technically
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33. Technical and Non-technical Evaluation
Technical aspects of evaluation include
Integration
Validation
Verification
Examples of non-technical issues include:
The marketing position of the component supplier
Maintenance support provided
Alternative solutions, etc
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34. Evaluation Methods Procurement-oriented requirements engineering:
Identify several component candidates.
Investigate these.
Reject those not compliant with the main requirements.
Continue with the evaluation of the reduced number of candidate components.
If necessary refine the requirements, and repeat the evaluation process.
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35. Evaluation Methods Continued
One scenario is to:
Search for an internally developed component.
If none suitable is found, continue by searching for an external component.
Criteria which may favor the selection of an external component :
Time-to-market
Production and maintenance costs,
Quality
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36. Evaluation of the Assembly
It is necessary to evaluate the assembly; evaluation of the individual components is not sufficient.
This implies that an investigation of the integration procedure may be a part of an evaluation.
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37. System Design
System specification and definition of the system architecture
The initial architecture will be a result of both the overall requirements and the choice of component model.
Many decisions related to the system design will be a consequence of the component model selected.
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38. System Design: Evolutionary Approach
Component selection procedure:
Selection of component candidates, followed by;
Consideration of the feasibility of different combinations of these.
Evolutionary approach:
To find the most appropriate and feasible combination of the component candidates. In this way the results of the design activity may be less predictable.
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39. System Implementation
Implementation by coding can be reduced to the creation of the “glue-code” and to component adaptation.
This effort is usually less than 50% of the total development effort.
Effort per line of glue-code is about three times the effort per line of the application’s code.
It may still be necessary to design and implement some components.
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40. System Integration Integration
Is the composition of the implemented and selected components to constitute the software system.
There are several other aspects to be taken into consideration, namely:
Component adaptation;
Reconfigurations of assemblies;
Emerging properties of assemblies integrated into the system.
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41. Integration Considerations
Component adaptation
In many cases a component must be adjusted to system requirements.
Reconfigurations of assemblies
Different assemblies (or composite components) can include common basic components. for re-configuring assemblies must exist.
Emerging properties
An important fact is that it is not possible to discover all the effects of a component until the integration is performed.
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42. Verification and Validation
Expressed by Boehm
Validation: are we building the right product ?
Verification: Are we building the product right ?
Component Validation and Verification
After a component is selected it should be tested to check that it functions in accordance with its specification.
We should also note that the component validation is strongly related to system validation.
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43. System Verification and Validation
System verification and validation process is similar to the processes for non-component-based systems.
The difference is that the implications of the processes may be different – new component requirements may emerge and it may happen that the selected components cannot meet the new requirements.
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44. System Operation Support and Maintenance
Components exist even at run-time, making it possible to:
Improve and maintain the system by updating or adding new components to the system.
Improve the system quicker and more flexibly.
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45. Operation and Support: Considerations
Maintenance procedures can be more complicated as it is not necessarily clear who:
Is supporting the system.
The system vendor is.
The component vendors are.
Components can be used by several other components introducing version incompatibilities.
The same problem may appear when we install a component package.
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46. Inconsistent Component Integration
Product P Version V1
Product P Version V2
Component A Version V1
Component A Version V2
Component B Version V1
Component B Version V2
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47. System Development Process
Consists of parallel tracks in which:
The basic architecture and its environment is being developed and managed concurrently with both the development of applications consisting of components and the evaluation of the actual components.
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48. Component-based Development Process
Analysis
Design
Implementation
Integration
Test
Evaluation
Find
Select
Adapt
Integrate
Test
System Development
Component evaluation
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49. Component Development
Requirements must be
captured
analyzed
defined
The component must be
designed
implemented
verified
validated
delivered
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50. Component Development Considerations
Components are built to be part of something else, thus:
There is greater difficulty in managing requirements;
Greater efforts are needed to develop reusable units;
A precise component specification is required
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51. Requirements Analysis and Definition
The development of reusable components would be easier if requirements remained constant during the time of component and system development.
As a result of new requirements for the systems old or new requirements for the components will emerge.
The more reusable a component is, the more demands are placed on it.
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52. Accumulated Component Requirements
Accumulated Requirements
Component
Product P1
Product P2
t-0
t-1
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53. Designing for Reusability
For a component to be reusable, it must be designed in a more general way than a component tailored for a unique situation.
Components intended to be reused requires adaptability. This will increase the size and complexity of the components
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54. Component Specification
It is important that the component be clearly and properly specified.
The consumer must be able to understand the component specification.
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55. Summary
In a component-based development process we distinguish development of components from development of systems using components:
Component development process: Is focused on building reusable units.
System development process: Concentrates on the reuse of components, their evaluation and integration.
These processes are often performed independently of each other.
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56. Summary Continued
To achieve a proper balance between the independence of and collaboration between the processes remains a challenge for researchers and practitioners
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