1. Unit 3. Engineering Component-Based Software: Processes and lifecycle
Component-Based Software Dr. Rami Bahsoon School of Computer Science The University Of Birmingham Office 112 Y9- Computer Science
Unit 3. Engineering Component-Based Software: Processes and lifecycle
Component-Based Software Engineering
Dr R Bahsoon

2. Unit 2 Learning Objectives
In this unit,
Unit 2.1
Quick review software development processes & lifecycle
Unit 2.2
Discuss software engineering challenges
Discuss reuse-software development and landscape
Appraise the benefits & limitations of reuse
Case study for orientation: Failure of Ariane 5
Introduces the component-based software lifecycle and contrast it to generic lifecycles
Component-Based Software Engineering
Dr R Bahsoon

3. Component-Based Software Engineering
Critical Question
How do you distinguish the process of
“Component Development” from that
of “Systems development with Components”?
Component-Based Software Engineering
Dr R Bahsoon

4. Component-Based Software Engineering
Unit 2.1 Overview of Software Processes
(Revision & Background)
Perhaps what you have seen from processes
looks explicitly at “Component Development”… and
implicitly at “Developing Software Systems from Components”
Component-Based Software Engineering
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5. Brainstorming Exercise
What is your understanding of a “Software Process”?
Have you used any “Software Process Model” in your practice?
Which models?
Examples?
Uses? Strengths/Weaknesses?
Observations?
Component-Based Software Engineering
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6. Component-Based Software Engineering
Objectives
Quick revision for software processes models (These are background material which you may have seen elsewhere)
Waterfall, incremental, evolutionary, spiral
Advantages and disadvantages
To describe the Rational Unified Process model
Component-Based Software Engineering
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7. Software Engineering – for Orientation
Software Engineering is a branch of systems engineering concerned with the development of large and complex software intensive systems. It focuses on:
the real-world goals for, services provided by, and constraints on such systems,
the precise specification of systems structure and behaviour, and the implementations of these specifications,
the activities required in order to develop an assurance that the specifications and real world-world goals have been met,
the evolution of these systems over time, and across systems families,
It is also concerned with the processes, methods and tools for the development of software intensive systems in an economic and timely manner.
Reference: A. Finkelstein
Component-Based Software Engineering
Dr R Bahsoon

8. Component-Based Software Engineering
Software Process
A structured set of activities required to develop a software system
Specification;
Design;
Validation;
Evolution.
A software process model is an abstract representation of a process. It presents a description of a process from some particular perspective.
Component-Based Software Engineering
Dr R Bahsoon

9. Process Models: Examples
The waterfall model
Separate and distinct phases of specification and development.
Evolutionary development
Specification, development and validation are interleaved.
Component-based software engineering
The system is assembled from existing components.
Component-Based Software Engineering
Dr R Bahsoon

10. Component-Based Software Engineering
Waterfall Model
Component-Based Software Engineering
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11. Waterfall Model Phases
Phase 1. Requirements analysis and definition
The process of establishing what services are required and the constraints on the system’s operation and development.
What is the system about?
Requirements engineering process
Feasibility study;
Requirements elicitation and analysis;
Requirements specification;
Requirements validation.
Phase 1
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12. Phase 1. Requirements Engineering process
Activities
Output
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13. Waterfall Model Phases
Phase 2. System and software design
i.e., How the requirements to be realised? Design a software structure that realises the specification;
Architectural design
Abstract specification
Interface design
Component design
Data structure design
Algorithm design…..
Phase 2
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14. The Software Design Process
Output
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15. Waterfall Model Phases
Phase 3. Implementation and unit testing
Implementation: Executable code
Unit testing (Component test)
Individual components (function/programs/classes) are tested independently;
Components may be functions or objects or coherent groupings of these entities.
Phase 3
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16. Waterfall Model Phases
Phase 4. Integration and system testing
System testing
Testing of the system as a whole. Testing of emergent properties is particularly important.
Acceptance testing
Testing with customer data to check that the system meets the customer’s needs.
Phase 4
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17. Waterfall Model Phases
Phase 5. Operation and maintenance
Phase 5
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18. Evolutionary Development
Exploratory development
Objective is to work with customers and to evolve a final system from an initial outline specification.
Start with well-understood requirements and add new features as proposed by the customer.
Throw-away prototyping
Objective is to understand the system requirements. Should start with poorly understood requirements to clarify what is really needed.
Component-Based Software Engineering
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19. Evolutionary Development
Component-Based Software Engineering
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20. Component-Based Software Engineering
Process Iteration
System requirements ALWAYS evolve in the course of a project so process iteration where earlier stages are reworked is always part of the process for large systems
Iteration can be applied to any of the generic process models (e.g., waterfall)
Two (related) approaches
Incremental delivery;
Spiral development.
Component-Based Software Engineering
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21. Incremental Development
Reference: A. Finkelstein
Component-Based Software Engineering
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22. Component-Based Software Engineering
Incremental Delivery
Rather than deliver the system as a single delivery,
the development and delivery is broken down into increments with each increment delivering part of the required functionality
User requirements are prioritised
highest priority requirements are included in early increments
Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve
Component-Based Software Engineering
Dr R Bahsoon

23. Incremental Development Advantages
Early increments act as a prototype to help elicit requirements for later increments
Lower risk of overall project failure
The highest priority system services tend to receive the most testing
Customer value can be delivered with each increment so system functionality is available earlier
Component-Based Software Engineering
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24. Component-Based Software Engineering
Spiral Development
Process is represented as a spiral rather than as a sequence of activities with backtracking
Each loop in the spiral represents a phase in the process
No fixed phases such as specification or design - loops in the spiral are chosen depending on what is required.
Risks are explicitly assessed and resolved throughout the process
Component-Based Software Engineering
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25. Component-Based Software Engineering
Spiral Model
Component-Based Software Engineering
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26. Component-Based Software Engineering
Spiral Model
Component-Based Software Engineering
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27. Component-Based Software Engineering
Spiral Model Sectors
Objective setting
Specific objectives for the phase are identified.
Risk assessment and reduction
Risks are assessed and activities put in place to reduce the key risks
Development and validation
A development model for the system is chosen which can be any of the generic models
Planning
The project is reviewed and the next phase of the spiral is planned
Component-Based Software Engineering
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28. Exercise -The Rational Unified Process
Use the Internet to understand RUP. Prepare a brief summary on RUP for class discussion
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29. Component-Based Software Engineering
RUP Model
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30. Component-Based Software Engineering
RUP- Phases
Inception
Establish the business case for the system
Elaboration
Develop an understanding of the problem domain and the system architecture
Construction
System design, programming and testing
Transition
Deploy the system in its operating environment
Component-Based Software Engineering
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31. Do you agree/disagree & Why? Component-Based Software Engineering
RUP- Class Discussion
It is claimed that RUP, if adopted, can:
Develop software iteratively,
Manage requirements,
Support component-based software development,
Verify software quality,
Control changes to software etc.
What do you think?
Do you agree/disagree & Why?
Component-Based Software Engineering
Dr R Bahsoon

32. Component-Based Software Engineering
Summary of Unit 2.1
Software processes are the activities involved in producing and evolving a software system
Software process models are abstract representations of these processes
General activities are specification, design and implementation, validation and evolution
Generic process models describe the organisation of software processes. Examples include the waterfall model, evolutionary development and component-based software engineering
Iterative process models describe the software process as a cycle of activities
The Rational Unified Process is a generic process model that separates activities from phases
Component-Based Software Engineering
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33. Unit 2 Learning Objectives
In this unit,
Unit 2.1
Quick review software development processes & lifecycle
Unit 2.2
Rational Unified Process
Model-driven development
Reuse-driven software development and landscape
Component-based software lifecycle
Component-Based Software Engineering
Dr R Bahsoon

34. Challenges in Software Engineering
Complexity
The size and complexity of software is increasing rapidly
Change, maintenance & continuous evolution
Users’ Requirements and the environment in which the software works are in continuous change…
Changes in non-functional requirements have global impact to threat software stability
Legacy systems: old and valuable systems must be maintained, updated, and be integrated with new systems
Software upgrades are expected after deployment…
Development and evolution costs for long-lifetime systems
System evolution
System development
Time
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35. Challenges in Software Engineering
Architecting dependable software
Software must be trustworthy by its users
Component-Based Software Engineering
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36. Challenges in Software Engineering
Single products become part of product family
Heterogeneity
Software that can cope with heterogeneous platforms and execution environments
E.g. Fixed distributed and mobile environments
Time to market
There is increasing pressure for faster delivery of software to gain competitive advantage
Component-Based Software Engineering
Dr R Bahsoon

37. Challenges in Software Engineering
Concentration on the business issues…
“Around 30% of the development effort is spent
on the infrastructure that add no value”
Component-Based Software Engineering
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38. Model Driven Development
The software development process is driven by the activity of modelling (with UML)
Supports full lifecycle: analysis, design, implementation, deployment, maintenance, evolution and integration with later systems
Builds in Interoperability and Portability
Lowers initial cost and maximises return-on-investment
Applies directly to the mix you face:
Programming language; Network; Operating system, Middleware
Component-Based Software Engineering
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39. The Model-Driven Process
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40. Component-Based Software Engineering
MDA Framework
A model is a description of a system.
A PIM describes a system without any knowledge of the final implementation platform.
A PSM describes a system with full knowledge of the final implementation platform.
A transformation definition describes how a model in a source language can be transformed into a model in a target language.
A transformation tool performs a transformation for a specific source model according to a transformation definition.
Component-Based Software Engineering
Dr R Bahsoon

41. PIM - Platform Independent Model
Model with a high level of abstraction independent of any implementing technology.
Specifies the system from the viewpoint of how it best supports the business.
Whether a system will be implemented on a mainframe with a relational database or on an EJB application server plays no role in a PIM.
Component-Based Software Engineering
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42. PSM – Platform Specific Model
A transformation of PIM tailored to specify a system in terms of the implementation constructs available in the chosen implementation technology
A PIM is transformed into one or more PSMs: for each specific technology platform a separate PSM is generated.
For example, an EJB PSM is a model of the system in terms of EJB structures.
It typically contains EJB specific terms like “home interface”, “entity bean”, “session bean” and so on.
A relational database PSM includes terms like “table”, “column”, “foreign key”, and so on.
Component-Based Software Engineering
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43. Component-Based Software Engineering
Code
The final step in the development is the transformation of each PSM to code.
A PSM fits its technology closely and so this transformation is relatively straightforward.
MDA defines the PIM, PSM, and code and also defines how these relate to each other.
Component-Based Software Engineering
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44. Tool Support & References
AndroMDA
An extensible open source generator framework that adheres to the Model Driven Architecture (MDA) paradigm.
Models from UML tools can be transformed into deployable components for your choice of platform (J2EE, Spring, .NET).
References:
OMG
Book by A. Kleppe et al., MDA Explained, Addison-Wesley, 2003
Component-Based Software Engineering
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45. Another Shift in Paradigm…
1970
1990
2000
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46. Component-Based Software Engineering
Shift in Effort…
Waterfall model 2 5 5 7 5 1 00
Specification
Design
Development
Integration and testing
Iterative development 2 5 5 7 5 1 00
Specification
Iterative development
System testing
Component-based software engineering 2 5 5 7 5 1 00
Specification
Development
Integration and testing
In CBSE much of the effort/cost are spent on
integration and testing…
Component-Based Software Engineering
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47. Systematic Software Reuse
In most engineering disciplines, systems are designed by composing existing components that have been used in other systems
Software engineering has been more focused on original development…
To achieve “potentially” better software, more quickly and at lower cost, we need to adopt a design process that is based on systematic software reuse...
Component-Based Software Engineering
Dr R Bahsoon

48. Reuse Approaches & Landscape
Component-Based Software Engineering
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49. Reuse Approaches & Landscape
Component-Based Software Engineering
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50. Component-Based Software Engineering
Benefits of Reuse
Component-Based Software Engineering
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51. Component-Based Software Engineering
Benefits of Reuse
Component-Based Software Engineering
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52. Component-Based Software Engineering
Problems with Reuse
Component-Based Software Engineering
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53. Component-Based Software Engineering
Problems with Reuse
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54. Component-Based Software Engineering
Case Study: Ariane 5
In 1996, the 1st test flight of the Ariane 5 rocket ended in disaster when the launcher went out of control 37 seconds after take off
The problem was due to a reused component from a previous version of the launcher (the Inertial Navigation System) that failed because assumptions made when that component was developed did not hold for Ariane 5
The functionality that failed in this component was not required in Ariane 5
Component-Based Software Engineering
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55. Component-Based Software Engineering
Case Study: Ariane 5
On June 4, 1996 Ariane 5 rocket launched by the European Space Agency exploded just forty seconds after its lift-off from French Guiana
The rocket was on its first voyage, after a decade of development costing $7 billion. The destroyed rocket and its cargo were valued at $500 million
A board of inquiry investigated the causes of the explosion and in two weeks issued a report
Component-Based Software Engineering
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56. Component-Based Software Engineering
Case study: Ariane 5
Software failure in the inertial reference system occurred when an attempt to convert a 64-bit floating point number to a signed 16-bit integer causing overflow.
Specifically a 64 bit floating point number relating to the horizontal velocity of the rocket with respect to the platform was converted to a 16 bit signed integer.
The number was larger than 32,767, the largest integer storeable in a 16 bit signed integer, and thus the conversion failed!
There was no exception handler associated with the conversion so the system exception management facilities were invoked. These shutdown the software!
REUSE!
System
Backup
Component-Based Software Engineering
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57. Component-Based Software Engineering
Based on systematic reuse where systems are integrated from existing components or COTS (Commercial-off-the-shelf) systems.
Process stages
Component analysis;
Requirements modification;
System design with reuse;
Development and integration.
Emphasis is on Reuse  Reuse-oriented development
This approach is becoming increasingly used as component standards have emerged.
Component-Based Software Engineering
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58. Reuse-Oriented Development
e.g. Ariane 5 doesn’t require the 64bit conversion…. Drop it!
Analyse written software
Do existing software/packages fit my need?
Component-Based Software Engineering
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59. Component-Based Software Engineering
The CBSE process
When reusing components,
It is essential to make trade-offs between ideal requirements and the services actually provided by available components.
This involves:
Developing outline requirements;
Searching for components then modifying requirements according to available functionality
Searching again to find if there are better components that meet the revised requirements.
Component-Based Software Engineering
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60. Component-Based Software Engineering
The CBSE process
Component-Based Software Engineering
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61. The Component Identification Process
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62. Component dentification issues
Trust.
You need to be able to trust the supplier of a component
At best, an untrusted component may not operate as advertised; at worst, it can breach your security
Requirements.
Different groups of components will satisfy different requirements
Validation.
The component specification may not be detailed enough to allow comprehensive tests to be developed.
Components may have unwanted functionality. How can you test this will not interfere with your application?
Component-Based Software Engineering
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63. Component composition
The process of assembling components to create a system
Composition involves integrating components with each other and with the component infrastructure
Normally you have to write ‘glue code’ to integrate components
Component-Based Software Engineering
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64. V Development Process for CBS
Software process
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65. V Development Process for CBS
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66. Component-Based Software Engineering
CBS Process
Component-Based Software Engineering
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67. Component-Based Software Engineering
CBS Process
Requirements: Requirements definition → use case model and business concept model
Specification: Component Identification, Component Interaction, and Component Specification
Provisioning: determine what components to build, buy or reuse
Assembly: guide correct integration of components, existing assets and suitable user interface → application that meets business needs
Theses phases replace analysis, design and implementation phases in processes like RUP.
Component-Based Software Engineering
Dr R Bahsoon

68. Component Identification
Component-Based Software Engineering
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69. Component Interaction
Component-Based Software Engineering
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70. Component-Based Software Engineering
Provisioning
Source component implementations either
by directly implementing the specification or
by finding an existing component that fits the specification
The component specification is as independent as possible from target technologies/platforms
Component-Based Software Engineering
Dr R Bahsoon