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Requirements Engineering

Requirements Engineering. CSCU 411 Ch 9. LEARNING OBJECTIVES. To understand that requirements engineering is a cyclical process involving three types of activity: elicitation, specification, and validation To appreciate the role of social and cognitive issues in requirements engineering

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Requirements Engineering

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  1. Requirements Engineering CSCU 411 Ch 9

  2. LEARNING OBJECTIVES • To understand that requirements engineering is a cyclical process involving three types of activity: elicitation, specification, and validation • To appreciate the role of social and cognitive issues in requirements engineering • To be able to distinguish a number of requirements elicitation techniques • To be aware of the contents of a requirements specification document • To Know various techniques and notations for specifying requirements • To be aware of different perspectives and aspects that may be distinguished in modeling requirements

  3. Library • List of books by… • List of books with XXXX in title • List of books an topic XXXX • List of books that arrived after a date

  4. Library • Store info on books ordered but not received • Store customer info and date books are due

  5. Library Design • System? • O/S • DBMS • User interface (terminals, PCs) How Many • Type of user • General • Members • Staff • Permissions • Read • Read/Write • PRINT

  6. Library Design • Size of DB • Search types • Growth • Limits? • Response time • Search results • Local • Other branches? • Cost • Software • Hardware • Training • Procedures change • Some staff become redundant • Is it worth it? • Non technical aspects

  7. Library Design • Requirements elicitation • Requirements specification • Requirements validation and verification

  8. Requirements Elicitation • Functionalism (objective-order) • Social-relativism (subjective-order) • Radical-structuralism (objective-correct) • Neohumanism (subjective-conflict) • Democratic • Network

  9. Requirements Elicitation Techniques

  10. Requirements Elicitation • Task Analysis • What normally happens • What we wish happened • What can happen • What we decide on • Scenarios

  11. Business Process Redesign (BPR) • 1. Identify processes for innovation. • 2. Identify change levers • 3. Develop process visions • 4. Understand the existing process • 5. Design and prototype

  12. THE REQUIREMENTS SPECIFICATION DOCUMENT • A requirements specification should be correct • A requirements specification should be unambiguous • A requirements specification should be complete • A requirements specification should be (internally) consistent • Requirements should be ranked for importance or stability • A requirements specification should be verifiable • A requirements specification should be modifiable • A requirements specification should be traceable

  13. THE REQUIREMENTS SPECIFICATION DOCUMENT • Details we must look at • Mode. Systems may behave differently depending on the mode of operation • User class. Different functionality Day be offered to different classes of users (login type) • Objects. Requirements may be classified according to the objects in the real world • Response. Some systems are best described by placing together functions that generate response • Functional hierarchy. When no other classification fits

  14. REQUIREMENTS SPECIFICATION TECHNIQUES • Noise • Silence • Over-specification • Contradictions • Ambiguity • Forward references • Wishful thinking

  15. Entity-Relationship Modeling

  16. State Machines

  17. Structured Analysis Design

  18. SADT and our Library

  19. A MODELING FRAMEWORK • The business perspective • The information perspective • The functionality perspective • The implementation perspective

  20. A MODELING FRAMEWORK • Consider the following: • Goals and constraints • Function In to Out • Fees • Members • (white Box) • Data • Types, attrib, relations, constraints • Organization • Structure • Quality of work • Technical Structure • Hardware • Users • Infrastructure • Distribution • Locations • Machines

  21. Verification and Validation • Checking against the requirements document • Correct • Complete • No ambiguity • Consistency

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