vu-re-lecture-10 requirement engineering.ppt
- 1. 1 Requirements Elicitation – 2 Lecture # 10
- 2. 2 Requirements Engineering Process Requirements Elicitation Requirements Analysis and Negotiation Requirements Specification Requirements Validation User Needs, Domain Information, Existing System Information, Regulations, Standards, Etc. Requirements Document Agreed Requirements
- 3. 3 Recap of Last Lecture - 1 • Introduced the concept of elicitation and requirements elicitation process • Basics of knowledge acquisition (reading, listening, asking, & observing) • Knowledge acquisition techniques (individual, group, modeling, cognitive) • Elicitation problems (scope, understandability, volatility)
- 4. 4 Recap of Last Lecture - 2 • Context (organization, environment, project, constraints imposed by people) • Guidelines for knowledge acquisition
- 5. 5 Components of Requirements Elicitation Business Context Stakeholder Needs and Constraints Application Domain Problem to be Solved
- 6. 6 Dimensions to Requirements Elicitation • Application domain understanding • Problem understanding • Business understanding • Understanding the needs and constraints of system stakeholders
- 7. 7 Dimensions to Requirements Elicitation - 2 • Application domain understanding – Knowledge of the general area where the system is applied • Problem understanding – The details of the specific customer problem where the system will be applied must be understood
- 8. 8 Dimensions to Requirements Elicitation - 3 • Business understanding – Understand how systems interact and contribute to overall business goals • Understanding the needs and constraints of system stakeholders – Understand, in detail, the specific needs of people who require system support in their work
- 9. 9 Elicitation and Analysis Processes • Requirements elicitation and requirements analysis are closely linked processes
- 10. 10 Requirements Elicitation Stages • Objective setting • Background knowledge acquisition • Knowledge organization • Stakeholder requirements collection
- 11. 11 Objective Setting • Overall organizational objectives should be established at this stage • These include general goals of business, an outline description of the problem to be solved and why the system may be necessary, and the constraints on the system such as budget, schedule, and interoperability constraints
- 12. 12 Background Knowledge Acquisition • Requirements engineers gather and understand background information • This includes information about the organization where the system is to be installed, information about the application domain of the system, and information about any existing systems which are in use and which may be replaced
- 13. 13 Knowledge Organization • The large amount of knowledge which has been collected in previous stage must be organized and collated • Identifying system stakeholders and their roles in the organization, prioritizing the goals of the organization and discarding domain knowledge which does not contribute directly to the system requirements
- 14. 14 Stakeholder Requirements Collection • It involves consulting system stakeholders to discover their requirements, and deriving requirements which come from the application domain and the organization which is acquiring the system
- 15. 15 A General Requirements Elicitation Process Establish Objectives Understand Background Organize Knowledge Collect Requirements Business goals Problem to be solved System constraints Organizational structure Application domain Existing systems Stakeholder identification Goal prioritization Domain knowledge filtering Stakeholder requirements Domain requirements Organizational requirements
- 16. 16 Comments on this Process - 1 • It is an idealized process, while the reality of requirements elicitation tends to be much messier • The activities are usually mixed up with each other • If objective setting activities are not carried out, significant analysis problems occur, as no objective and business goals are available to prioritize requirements
- 17. 17 Comments on this Process - 2 • The output from the requirements elicitation process should be a draft document which describes the system requirements, which is then analyzed to discover problems and conflicts in the requirements definition • This process is followed by the requirements analysis process, which will be discussed in another lecture
- 18. 18 Basics of Knowledge Acquisition • Reading • Listening • Asking • Observing • Results in large volume of information, which must be organized to make it understandable
- 19. 19 Knowledge Structuring Techniques • Partitioning • Abstraction • Projection
- 20. 20 Partitioning • Organization of knowledge into aggregation relationships, where requirements knowledge is described in terms of its parts • Booking system example: a booking record may be may be defined as a flight reference, source & destination of flight, the name & address of the passenger, fare, and date of travel
- 21. 21 Abstraction • Organization of knowledge according to general/specific relationships. Requirement knowledge is described by relating specific instances to abstract structures • Passenger abstraction may represent all classes of passengers (children, adults, full- fare paying, concessionary passengers, etc.)
- 22. 22 Projection • Organization of knowledge from several different perspectives or viewpoints • Booking system example: travel agents, airline management, check-in desk operators, passengers, a bookings database, etc.
- 23. 23 Next Lecture • There are various techniques of requirements elicitation which may be used including – Interviewing – Scenarios – Prototyping – Participant observation
- 24. 24 Summary • Requirements elicitation involves understanding the application domain, the specific problem to be solved, the organizational needs and constraints and the specific facilities needed by system stakeholders • The processes of requirements elicitation, analysis and negotiation are iterative, interleaved processes which must usually be repeated several times
- 25. 25 References • ‘Requirements Engineering: Processes and Techniques’ by G. Kotonya and I. Sommerville, John Wiley & Sons, 1998 • Software Requirements: Objects, Functions, and States by A. Davis, PH, 1993