SOFT 423: Software Requirements

Transcription

1 SOFT 423: Software Requirements Week 1 Class 3 Requirements Process SOFT 423 Winter

2 Last Class What are Requirements Requirements Eng vs. System Analysis Requirements Eng vs. Design Classes of Custom Systems Analysis Elicitation Stakeholders SOFT 423 Winter

3 Sample Problems The system shall provide an easy-to-use graphical user interface based on MS Windows 95 SOFT 423 Winter

4 Sample Problems The system shall provide an easy-to-use graphical user interface based on MS Windows 95 what does easy to use mean? easy to use for who ambiguous Windows 95? SOFT 423 Winter

5 Sample Problems Accredited uses should have privileged access to the cataloguing facilities of the system. SOFT 423 Winter

6 Sample Problems Accredited uses should have privileged access to the cataloguing facilities of the system. accredited user defined elsewhere? privileged access defined elsewhere? SOFT 423 Winter

7 Sample Problems Software system shall be implemented using three separate modules for cataloging, user access and archiving. SOFT 423 Winter

8 Sample Problems Software system shall be implemented using three separate modules for cataloging, user access and archiving. premature design SOFT 423 Winter

9 Sample Problems List the possible stake holders for a library cataloging system SOFT 423 Winter

10 Sample Problems List the possible stake holders for a library cataloging system Library Users Cataloging Staff Library Management Help Desk Book publishers (indirect) Systems developers Managers of other library automation systems SOFT 423 Winter

11 This Class Requirements Process SOFT 423 Winter

12 Design SOFT 423 Winter

13 Design Processes involves: creativity interactions between different people technical/engineering judgment background knowledge and experience inputs are not precisely defined difficult to automate cannot be specified in detail SOFT 423 Winter

14 Design Processes examples: game design organizing a conference producing a record requirements engineering SOFT 423 Winter

15 Design - The Term Design used in many ways external design -> requirements internal design -> design step of software engineering Decomposition and Modelling decomposition and modelling of problem domain or existing systems -> requirements decomposition and modelling of solution system -> internal design SOFT 423 Winter

16 Requirements Engineering Process SOFT 423 Winter

17 Requirements Engineering Process [Bray] Existing System Information Stakeholder Needs Organizational Standards Regulations Domain Information Requirements Engineering Process Requirements Document System Specification HCI Specification SOFT 423 Winter

18 Process Inputs Existing systems information Systems to be replaced (may not be software) Space Shuttle Mission Computer Conference Registration System Systems that interact with new system magnetic anomaly detector bar code readers SOFT 423 Winter

19 Process Inputs Stakeholder needs Description of stakeholder needs help system for users enrolment statistics for BIU funding marks for students class enrollment for professors and room reservations Remember indirect stakeholders!! SOFT 423 Winter

20 Process Inputs Organizational Standards Standards used in an organization for system development, testing, quality management, etc. Hardware platform specifications Software platform specifications product testing requirements SOFT 423 Winter

21 Process Inputs Regulations Regulations imposed by external agencies Minimum time to serve food in a fast-food restaurant Minimum/Maximum temperatures for storing food aviation air worthiness regulations data protection/privacy security interest calculation regulations data precision regulations SOFT 423 Winter

22 Process Inputs Domain Information Information about the application domain for the system UPC symbols are a 6 digit manufacture code a 5 digit item code and 1 check digit for UPC coupons the item code is a 3 digit family code and a 2 digit value code full time students take minimum of 3 classes per term SOFT 423 Winter

23 Process Outputs Requirements Document system requirements understandable to stakeholders System specifications more details for some of the system functionality (may need explaining to stakeholders) HCI Specification User Interface Details SOFT 423 Winter

24 Requirements Engineering Process [Bray] Existing System Information Stakeholder Needs Questions Understanding, Questions Analysis Organizational Standards Elicitation Elicitation Notes Regulations Domain Information Suggested New System Behaviour, Questions Specification HCI SOFT 423 Winter

25 Requirements Engineering Process [Bray] PD details +Requirements Analysis Requirements Document Elicitation Notes Requested Behaviour + Constraints Specification Specification Document HCI HCI Document SOFT 423 Winter

26 Requirements Engineering Process [Bray] Analysis PD details +Requirements Requirements Document Elicitation Notes understanding Specification Specification Document HCI HCI Document SOFT 423 Winter

27 Requirements Engineering Process [Bray] Elicitation Notes Requested Behaviour + Constraints Analysis understanding Specification Behaviour Requirements Document PD details +Requirements Specification Document HCI HCI Document SOFT 423 Winter

28 What about Validation? Not present in this process model Pervasive Other requirements process models have explicit validation steps SOFT 423 Winter

29 Alternative Process Model SOFT 423 Winter

30 Spiral Model of Requirements Process Requirements Elicitation Requirements Conflict and Negotiation Requirements Validation Requirements Documentation SOFT 423 Winter

31 Spiral Model of Requirements Process Requirements Elicitation Informal Statement of Requirements Requirements Conflict and Negotiation Requirements Validation Requirements Documentation SOFT 423 Winter

32 Spiral Model of Requirements Process Requirements Elicitation Requirements Conflict and Negotiation Agreed Requirements Requirements Validation Requirements Documentation SOFT 423 Winter

33 Spiral Model of Requirements Process Requirements Elicitation Requirements Conflict and Negotiation Requirements Validation Requirements Documentation Draft Requirements Document SOFT 423 Winter

34 Spiral Model of Requirements Process Requirements Elicitation Req Doc & Validation Report Requirements Conflict and Negotiation Requirements Validation Requirements Documentation SOFT 423 Winter

35 Process Variability SOFT 423 Winter

36 Process Variability different people execute the process different ways shortcuts based on past knowledge reuse specifications experience of personnel same person does it different ways recognition of special circumstances new software adjust processes to software environment influence deadlines SOFT 423 Winter

37 Process Variability Processes vary from one organization to another systematic to unstructured Factors: technical maturity discipline involvement organizational culture application domain Rate Requirements and Constraints essential, desirable, useful SOFT 423 Winter

38 Data SOFT 423 Winter

39 Data Systems manipulate data some data is part of interaction with the environment Problem Data vs Solution Data both interact with the environment problem data is from problem domain solution data part of solution introduced by the solution e.g. User Interface Dialog Information still part of requirements more malleable SOFT 423 Winter

40 Modelling Data As part of requirements we will build a model of the environment Solution system may also have a model of some portion of the environment Easy to get confused between the two models design concern, not requirements concern, but something to be aware of SOFT 423 Winter

41 Modelling Data Example - Library System - Patron Patron is a direct stakeholder borrows books, fees?, needs to search for books modelled part of problem domain Also part of solution system Library Card ID, Fees, Fines System model will contain some subset of the PD model (+ other implementation issues too) SOFT 423 Winter

42 Next Class Elicitation SOFT 423 Winter