Chapter 5 ComponentBased Development Process Building Reliable Componentbased

Chapter 5 Component-Based Development Process Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 1

Overview q Software Process Models q Component-based Development q Component-Based Software Lifecycle q Summary Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 2

Purpose q This chapter: l Describes the component-based software lifecycle. l Provides an overview of generic software engineering processes. l Motivates the need for specific processes when developing components and when building systems or applications from components l Describe these processes, reviewing their procedures. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 3

Software Process Models q Generic lifecycle activities q The Sequential Model q Evolutionary Development q Unified Process Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 4

Generic lifecycle activities q Activities l Requirements analysis and system specification l System and software design l Implementation and unit testing l Integration, system verification and validation l Operation support and Maintenance l Disposal Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 5

The Sequential Model Analysis ve De en pm lo Design t Implementation Integration Test Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 6

Evolutionary Development q Develop a system gradually in many repetitive stages: l Increasing the knowledge of the system requirements and system functionality in each stage l exposing the results to user comments. q This can be achieved by using: l The Iterative Model l The Incremental Model l The Prototyping Model Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 7

The Iterative Model Analysis De ve lo pm Design en t Implementation Integration Test Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 8

The Incremental Model Increment 1 2. . . n De t en pm lo ve Analysis Design Implementation Integration Test Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 9

The Prototyping Model Test prototype De ve lo Analysis pm Design en t Develop prototype Implementation Integration Test Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 10

Unified Process q Inception l The first phase in which the system is described in a formalized way, providing a base for further development. q Elaboration l The phase in which the system architecture is defined and created. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 11

Unified Process continued q Construction l The development of completely new products, with reuse capabilities. q Transition l The work of delivering the product to the customer. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 12

Unified Process Illustrated Phases Inception Elaboration Construction Transition Requirements An iteration in the elaboration phase Analysis Design Implementation Test Iter #1 Iter #2 --- --- --- Iter #n Iterations Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 13

Component-based Development q Reuse Approach q Separation of Development Processes q Component-based Development (CBD) – The Consumer Perspective q Component Development (CD) – The Producer Perspective Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 14

Reuse Approach q The reuse approach makes the following assumptions: l All experience can be reused. l Reuse typically requires some modification of objects being reused. l Reuse must be integrated into the specific software development. l Analysis is necessary to determine when, and if, reuse is appropriate. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 15

Reuse q For given requirements r for an object x, we propose the reuse of the already existing object xk. The reuse procedure includes: l Identification of a set of objects x 1 , x 2 … xm as candidates, l Selection of one of these, and, if required, l Its modification to translate xk to x’ which is as close to x as possible. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 16

Reuse continued q The object x can be of any type: l A system architecture l An overall design l A design pattern l An infrastructure l Different types of components or services. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 17

Separation of Development Processes Component development System development with components q System development with components l Focuses on the identification of reusable entities and relations between them, beginning from the system requirements and from the availability of components already existing. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 18

Component Guidelines q Components are built to be used and reused in many applications and should thus be: l Well specified l Easy to understand l Sufficiently general l Easy to adapt l Easy to deliver and deploy l Easy to replace Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 19

CBD – The Consumer Perspective q Typically a component consumer selects a component and then uses it in a software system. q The component lifecycle must be considered in relation to the lifecycle of the system as a whole. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 20

The Consumer Perspective Continued q Common considerations: l Will the component producer be able to deliver a new component version when this is required? l How will changes in a component in the system affect the behavior of another component? l Will the component be compatible with newer versions of the surrounding systems and applications? Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 21

CD – The Producer Perspective q The producer of a component must take into consideration: l The business goal l Component functionality l Maintenance policy l The type of application and system in which the component will be used l The requirements of the system l The life expectancy of relevant systems Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 22

Disposal q Disposal of Component-based Systems generally takes place due to two different factors: l Dissatisfaction l Obsolescence Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 23

Disposal: Dissatisfaction q Initiated by consumers when they conclude that: l The component no longer provides the support of the system it was intended to provide or; l That the system no longer needs the component. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 24

Disposal: Obsolescence q When a component becomes obsolete and the producer ceases component maintenance and operation support. q This is likely to occur when: l A new, more effective component with the same, similar or extended functionality is found. l The producer is not able to continue with support or maintenance. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 25

Disposal: Considerations q Both producer and consumer should arrive at a compromise with respect to the lifecycles of their different products. q The consumer should always have in mind an alternative solution, such as: l The replacement of the component with another developed internally or by another producers. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 26

Component-Based Software Lifecycle q Development With Components q Requirements Analysis and Definition q Component Selection and Evaluation q System Design q System Implementation q System Integration q Verification and Validation q System Operation Support and Maintenance q System Development Process Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 27

Development With Components q Emphasis is placed on the reuse of pre-existing components, rather than on the implementation of the system designed. q First l Find reusable units which will meet the requirements specified and will be compliant with the system design. q Second l Determine the amount of extra effort required to use reusable units instead of units dedicated to a particular purpose. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 28

Requirements Analysis and Definition q The three analysis tasks: l Capture the system requirements and define the system boundaries. l Define the system architecture to permit component collaboration. l Define component requirements to permit the selection or development of the required components. q The approach is: l optimistic and an idealized view of the process. l It assumes that the component requirements can be precisely defined and that it is possible to find components Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 29

Analysis and Definition Continued q Not finding a component which exactly satisfies the requirements necessitates the development of a new component. q The process of design and even requirements engineering will be combined with component selection and the evaluation process. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 30

Component Selection and Evaluation q The components selected must therefore be evaluated: l Technically l Non-technically Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 31

Technical and Non-technical Evaluation q Technical aspects of evaluation include l Integration l Validation l Verification q Examples of non-technical issues include: l The marketing position of the component supplier l Maintenance support provided l Alternative solutions, etc Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 32

Evaluation Methods q Procurement-oriented requirements engineering: 1. Identify several component candidates. 2. Investigate these. 3. Reject those not compliant with the main requirements. 4. Continue with the evaluation of the reduced number of candidate components. 5. If necessary refine the requirements, and repeat the evaluation process. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 33

Evaluation Methods Continued q One scenario is to: 1. Search for an internally developed component. 2. If none suitable is found, continue by searching for an external component. q Criteria which may favor the selection of an external component : l Time-to-market l Production and maintenance costs, l Quality Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 34

Evaluation of the Assembly q It is necessary to evaluate the assembly; evaluation of the individual components is not sufficient. l This implies that an investigation of the integration procedure may be a part of an evaluation. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 35

System Design q System specification and definition of the system architecture l The initial architecture will be a result of both the overall requirements and the choice of component model. l Many decisions related to the system design will be a consequence of the component model selected. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 36

System Design: Evolutionary Approach q Component selection procedure: l Selection of component candidates, followed by; l Consideration of the feasibility of different combinations of these. q Evolutionary approach: l 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. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 37

System Implementation q Implementation by coding can be reduced to the creation of the “glue-code” and to component adaptation. l This effort is usually less than 50% of the total development effort. l Effort per line of glue-code is about three times the effort per line of the application’s code. q It may still be necessary to design and implement some components. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 38

System Integration q Integration l Is the composition of the implemented and selected components to constitute the software system. q There are several other aspects to be taken into consideration, namely: l Component adaptation; l Reconfigurations of assemblies; l Emerging properties of assemblies integrated into the system. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 39

Integration Considerations q Component adaptation l In many cases a component must be adjusted to system requirements. q Reconfigurations of assemblies l Different assemblies (or composite components) can include common basic components. for re-configuring assemblies must exist. q Emerging properties l An important fact is that it is not possible to discover all the effects of a component until the integration is performed. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 40

Verification and Validation q Expressed by Boehm l Validation: are we building the right product ? l Verification: Are we building the product right ? q Component Validation and Verification l After a component is selected it should be tested to check that it functions in accordance with its specification. l We should also note that the component validation is strongly related to system validation. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 41

System Verification and Validation q System verification and validation process is similar to the processes for non-component-based systems. q 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. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 42

System Operation Support and Maintenance q Components exist even at run-time, making it possible to: l Improve and maintain the system by updating or adding new components to the system. l Improve the system quicker and more flexibly. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 43

Operation and Support: Considerations q Maintenance procedures can be more complicated as it is not necessarily clear who: l Is supporting the system. l The system vendor is. l The component vendors are. q Components can be used by several other components introducing version incompatibilities. q The same problem may appear when we install a component package. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 44

Inconsistent Component Integration Product P Version V 1 Component A Version V 1 Component B Version V 1 Product P Version V 2 Component A Version V 2 Component B Version V 2 Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 45

System Development Process q Consists of parallel tracks in which: l 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. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 46

Component-based Development Process Analysis Find Implementation ua Adapt tio n Integrate Integration Test Component evaluation t en pm al lo Ev ve De Design Select System Development Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 47

Component Development q Requirements must be l captured l analyzed l defined q The component must be l designed l implemented l verified l validated l delivered Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 48

Component Development Considerations q Components are built to be part of something else, thus: l There is greater difficulty in managing requirements; l Greater efforts are needed to develop reusable units; l A precise component specification is required Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 49

Requirements Analysis and Definition q The development of reusable components would be easier if requirements remained constant during the time of component and system development. l As a result of new requirements for the systems old or new requirements for the components will emerge. l The more reusable a component is, the more demands are placed on it. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 50

Accumulated Component Requirements Accumulated Requirements Component Product P 1 Product P 2 t-0 t-1 Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 51

Designing for Reusability q For a component to be reusable, it must be designed in a more general way than a component tailored for a unique situation. q Components intended to be reused requires adaptability. This will increase the size and complexity of the components Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 52

Component Specification q It is important that the component be clearly and properly specified. q The consumer must be able to understand the component specification. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 53

Summary q In a component-based development process we distinguish development of components from development of systems using components: l Component development process: Is focused on building reusable units. l System development process: Concentrates on the reuse of components, their evaluation and integration. q These processes are often performed independently of each other. Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 54

Summary Continued q To achieve a proper balance between the independence of and collaboration between the processes remains a challenge for researchers and practitioners Building Reliable Component-based Systems Chapter 5 - Component-Based Development Process Page 55