vu-re-lecture-09 engineering requiremen.ppt
- 1. 1 Requirements Elicitation – 1 Lecture # 9
- 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 Requirements Elicitation - 1 • Elicit means to gather, acquire, extract, and obtain, etc. • Requirements elicitation means gathering requirements or discovering requirements
- 4. 4 Requirements Elicitation - 2 • Activities involved in discovering the requirements for the system
- 5. 5 Basics of Knowledge Acquisition • Reading • Listening • Asking • Observing These are the sources of knowledge acquisition
- 6. 6 Requirements Elicitation Techniques • Individual • Group • Modeling • Cognitive
- 7. 7 Problems in Requirements Elicitation • Problems of scope • Problems of understanding • Problems of volatility
- 8. 8 Problems of Scope • The boundary of the system is ill- defined • Unnecessary design information may be given
- 9. 9 Problems of Understanding - 1 • Users have incomplete understanding of their needs • Users have poor understanding of computer capabilities and limitations • Analysts have poor knowledge of problem domain
- 10. 10 Problems of Understanding - 2 • User and analyst speak different languages • Ease of omitting “obvious” information • Conflicting views of different users • Requirements are often vague and untestable, e.g., “user-friendly” and “robust”
- 11. 11 Problems of Volatility • Requirements evolve over time and hence there are some requirements which are bound to change during the system development process due to one reason or the other.
- 12. 12 Contexts in Requirements Elicitation Process • Organization • Environment • Project • Constraints imposed by people It is important to consider the context in which requirements are being elicited. Requirements elicitation process may be followed in the following contexts
- 13. 13 Contexts in Requirements Elicitation Process - 1 • Organization – Submitters of input – Users of output – Ways in which the new system change the business process
- 14. 14 Contexts in Requirements Elicitation Process - 2 • Environment – Hardware and software – Maturity of the target system domain – Certainty of the target system’s interfaces to the larger system – The target system’s role in the larger system
- 15. 15 Contexts in Requirements Elicitation Process - 3 • Project – The attributes of the different stakeholder communities, such as the end users, sponsors, developers, and requirements analysts. Examples of such attributes are: • Management style • Management hierarchy • Domain experience • Computer experience
- 16. 16 Contexts in Requirements Elicitation Process - 4 • The constraints imposed by the people – They are involved in the elicitation process, e.g., managerial constraints concerning cost, time, and desired quality in the target system
- 17. 17 Requirements Elicitation Guidelines - 1 • Assess the business and technical feasibility for the proposed system • Identify the people who will help specify requirements and understand their organizational bias • Define the technical environment • Identify “domain constraints” that limit the functionality or performance of the system
- 18. 18 Requirements Elicitation Guidelines - 2 • Define one or more requirements elicitation methods (interviews, focus groups, team meetings) • Solicit participation from many people so that requirements are defined from different points of view; be sure to identify the rationale for each requirement that is recorded
- 19. 19 Requirements Elicitation Guidelines - 3 • Identify ambiguous requirements as candidates for prototyping • Create usage scenarios to help customers/users better identify requirements
- 20. 20 Ethnomethodology • Looks for behaviors that may be different in a specific culture but which have the same underlying purpose or meaning • Conversational analysis • Measurement of body system functions • Non-verbal behavior studies • Detailed video analysis
- 21. 21 Requirements and Psychology • Errors in statements can happen in two places – Perception of facts – reality – Linguistic representation of one of these perceptions – personal reality • To remove these errors, requirements should be reviewed (during and after elicitation)
- 22. 22 Use Case Modeling • Define actors and black-box use cases • The functional requirements of the system are defined in terms of use cases and actors • The use case descriptions are a behavioral view
- 23. 23 Summary - 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)
- 24. 24 Summary - 2 • Context (organization, environment, project, constraints imposed by people) • Guidelines for knowledge acquisition
- 25. 25 References • ‘Requirements Engineering: Processes and Techniques’ by G. Kotonya and I. Sommerville, John Wiley & Sons, 1998