1. S/W Project Management Software Process Models

2. Objectives To understand  Software process and process models, including the main characteristics of each model, critical software process issues, and the pros and cons of each model.  The generic process activities and what they mean. This includes details of what exactly each activity is for and the stages within them. S/W Process Models 2

3. The 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. S/W Process Models 3

4. Abstraction Elimination of unnecessary detail  Model  Abstract view  Abstract representation S/W Process Models 4

5. Software Process model A software process model is an abstract representation of a process. It presents a description of a process from some particular perspective. No universal software process Highly intellectual Must dynamically adjust to creative needs of professionals and tasks S/W Process Models 5

6. Critical Software Process Issues Factors to consider  Nature of the project.  Software projects are different.  Organizational needs.  Experience level of members/team  Current product status  E.g., Brand new product?  Available tools and facilities S/W Process Models 6

7. Critical Software Process Issues Factors to consider  Quality  More intensive quality assurance  Product Technology  New technology or algorithm?  Requirements instability  Unknown requirements  Unstable requirements  Complexity  Large systems S/W Process Models 7

8. Software Process Models Waterfall V Spiral Rapid Application Development S/W Process Models 8

9. Waterfall model S/W Process Models 9

10. Waterfall model phases Requirements analysis and definition System and software design Implementation and unit testing Integration and system testing Operation and maintenance The main drawback of the waterfall model is the difficulty of accommodating change after the process is underway. One phase has to be complete before moving onto the next phase. S/W Process Models 10

11. Waterfall model problems Inflexible partitioning of the project into distinct stages makes it difficult to respond to changing customer requirements. Therefore, this model is only appropriate when the requirements are well-understood and changes will be fairly limited during the design process. Few business systems have stable requirements. Requirements have to be understood early on. S/W Process Models 11

12. V-Shaped Model Project and Requirements Planning Product Requirements and Specification Analysis Architecture or High-Level Design Detailed Design Unit Testing Integration and Testing System and Acceptance Testing Coding Production Operation and Maintenance S/W Process Models 12

13. V-Shaped Model  A variation of the Waterfall model.  Places strong emphasis on Verification and Validation.  Testing of the product is planned in the early phases of the process.  Acceptance test plan is developed.  System test plan is developed. S/W Process Models 13

14. V-Shaped Model  Emphasizes the relationship between the phases preceding and following coding.  The dotted lines indicate that these phases should be considered in parallel. S/W Process Models 14

15. Phases in the V-Shaped Model  Project and requirements planning –Determines system requirements and allocation of resources.  Product requirements and specification analysis –Analysis of software problem, concludes with complete specification of the software. S/W Process Models 15

16. Phases in the V-Shaped Model  Architecture or High-level design –Determines how the software functions are to implement the design.  Detailed Design –Defines algorithms for components that were defined during the architecture phase. S/W Process Models 16

17. Phases in the V-Shaped Model  Coding –Transforms the algorithms defined during the design phase into software.  Unit Testing –Checks each code module for errors. S/W Process Models 17

18. Phases in the V-Shaped Model  Integration and Testing –Integrate and test individual code modules.  System and acceptance testing –Test entire software system in its hardware environment. S/W Process Models 18

19. Phases in the V-Shaped Model  Productions, operation and maintenance –Puts software into production and provides for enhancements and corrections. S/W Process Models 19

20. V-Shaped Model Problems Does not easily handle concurrent events No iteration of phases Cannot handle dynamic changes in requirements throughout the life cycle Requirements are tested too late to make changes without affecting the schedule No risk analysis S/W Process Models 20

21. 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. S/W Process Models 21

22. S/W Process Models 22 Spiral model of the software process Determine objectives, alternatives and constraints Evaluate alternatives, identify, resolve risks Develop, verify next-level product Plan next phase And test plan requirements Operational prototype Risk analysis Risk analysis Risk analysis Risk analysis Proto- type 1 Prototype 2 Prototype 3 Opera- tional protoype Concept of Operation Simulations, models, benchmarks S/W requirements Requirement validation Design V&V Product design Detailed design Code Unit test Integration test Acceptance test Service Integration and test plan Development plan Requirements plan Life-cycle plan REVIEW

23. 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. S/W Process Models 23

24. Spiral Model problems Highly dependent on risk analysis  Requires very knowledgeable personnel  Errors may occur if risk is not properly analyzed Willingness of the Customer S/W Process Models 24

25. RAD Model Rapid Application Development User is involved in all phases Use tools that allow product evaluation at all stages of development Characterized by quick turnaround time from requirements definition to delivery High component reuse factor S/W Process Models 25

26. RAD Model Development Effort Time Requirements Planning User Description Construction Cut Over User Involvement S/W Process Models 26

27. Phases in RAD Model  Requirements planning phase –Requirements are gathered using technique called joint requirements planning (JRP)  User description –Joint application design (JAP) is used to harness user involvement. S/W Process Models 27

28. Phases in RAD Model  Construction phase –Combines design, coding, testing. Heavy use of code generators and other production tools  Cut over –Acceptance testing, installation and user training. S/W Process Models 28

29. Strengths of RAD Use of powerful tools reduces cycle time Lower cost due to reduced cycle time Ongoing customer involvement Reuse of existing program component S/W Process Models 29

30. RAD problems Heavily dependent on user involvement throughout the process. Requires highly skilled developers in the use of development tools. Heavily dependent on reusable components. S/W Process Models 30

31. Generic activities Specification Design (and implementation) Validation Evolution S/W Process Models 31

32. Specification The process of establishing what services are required and the constraints on the system’s operation and development. Requirements engineering process  Feasibility study;  Requirements elicitation and analysis;  Requirements specification;  Requirements validation. S/W Process Models 32

33. Example requirements engineering process S/W Process Models 33

34. Design and implementation The process of converting the system specification into an executable system. design  Design a software structure that realises the specification; Implementation  Translate this structure into an executable program; The activities of design and implementation are closely related and may be inter-leaved. S/W Process Models 34

35. Example design process activities Architectural design Abstract specification Interface design Component design Data structure design Algorithm design S/W Process Models 35

36. Example software design process S/W Process Models 36

37. Validation Verification and validation (V & V) is intended to show that a system conforms to its specification and meets the requirements of the system customer. Involves checking and review of processes, various testing stages. Testing involves executing the system with test cases that are derived from the specification. Testing tries to establish if observed behaviour matches expected behaviour. S/W Process Models 37

38. Testing stages Unit testing  Individual components are tested independently;  Components may be functions or objects or coherent groupings of these entities. Integration testing (subsystem testing)  Individual components are merged and tested. 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. S/W Process Models 38

39. Testing phases note that model is V S/W Process Models 39

40. Evolution Software is inherently flexible and can change. As requirements change through changing business circumstances, the software that supports the business must also evolve and change. Although there has been a demarcation between development and evolution (maintenance) this is increasingly irrelevant as fewer and fewer systems are completely new. S/W Process Models 40

41. Example evolution process S/W Process Models 41