CS540 Software Design Lecture 5 1 Lecture 5: High Level Requirements Specification Anita S. Malik Adapted from Schach (2004) Chapter 10

CS540 Software Design 2Lecture 5 Requirements Phase Process of discovering the client’s requirements Process of discovering the client’s requirements Misconception Misconception Must determine what client wants Must determine what client wants “I know you believe you understood what you think I said, but I am not sure you realize that what you heard is not what I meant!” “I know you believe you understood what you think I said, but I am not sure you realize that what you heard is not what I meant!” Must determine client’s needs Must determine client’s needs Familiarity with application domain Familiarity with application domain

CS540 Software Design 3Lecture 5 Requirements Analysis Techniques Interviewing (primary technique) Interviewing (primary technique) Structured interviews Structured interviews unstructured interviews unstructured interviews Questionnaires Questionnaires Forms analysis Forms analysis Video cameras Video cameras Use Cases/Scenarios Use Cases/Scenarios Rapid prototyping Rapid prototyping

CS540 Software Design 4Lecture 5 Interviews Structured Interviews: Specific pre-planned close ended questions are posed e.g., ‘How many….’, ‘How often….’, ‘How fast….’ Structured Interviews: Specific pre-planned close ended questions are posed e.g., ‘How many….’, ‘How often….’, ‘How fast….’ Unstructured Interviews: Open-ended questions are asked e.g., ‘What do you think about….’ Unstructured Interviews: Open-ended questions are asked e.g., ‘What do you think about….’ Interviewer prepares a written report outlining the results of the interview Interviewer prepares a written report outlining the results of the interview

CS540 Software Design 5Lecture 5 Scenarios Scenarios are another widely used technique for requirements elicitation Scenarios are another widely used technique for requirements elicitation Includes expected sequence of events as well as all exceptions Includes expected sequence of events as well as all exceptions List actions comprising the scenario, a storyboard, series of diagrams depicting the sequence of events etc. are some techniques used for depicting scenarios List actions comprising the scenario, a storyboard, series of diagrams depicting the sequence of events etc. are some techniques used for depicting scenarios Starting state, expected sequence of events, finishing state and exceptions to the expected sequence Starting state, expected sequence of events, finishing state and exceptions to the expected sequence Use Cases are widely used form of scenarios: pre conditions, normal flow, post conditions (Discussed in detail in Object-Oriented Analysis) Use Cases are widely used form of scenarios: pre conditions, normal flow, post conditions (Discussed in detail in Object-Oriented Analysis)

CS540 Software Design 6Lecture 5 Rapid Prototype Hastily built (“rapid”) Hastily built (“rapid”) Key functionality Key functionality What the client sees What the client sees Experimentation and change Experimentation and change

CS540 Software Design 7Lecture 5 Human Factors Client and intended users must interact with the user interface Client and intended users must interact with the user interface Human-computer interface (HCI) Human-computer interface (HCI) Menu, not command line Menu, not command line “Point and click” “Point and click” Windows, icons, pull-down menus Windows, icons, pull-down menus Human factors must be taken into account Human factors must be taken into account Lengthy sequence of menus Lengthy sequence of menus Expertise level of interface Expertise level of interface Uniformity of appearance Uniformity of appearance Advanced psychology vs. common sense? Advanced psychology vs. common sense? Rapid prototype of HCI obligatory Rapid prototype of HCI obligatory

CS540 Software Design 8Lecture 5 Rapid Prototype as Specification Technique No specification phase No specification phase Rapid prototype replaces specification document Rapid prototype replaces specification document

CS540 Software Design 9Lecture 5 Rapid Prototyping as Specification Technique Specifications: Rapid prototype plus list of additional features Specifications: Rapid prototype plus list of additional features Advantages Advantages Speed Speed No ambiguities, omissions, contradictions No ambiguities, omissions, contradictions Disadvantages Disadvantages Specification document is contract Specification document is contract Testing requires specifications Testing requires specifications Maintenance requires specifications Maintenance requires specifications Conclusion: Do not use rapid prototype as specifications Conclusion: Do not use rapid prototype as specifications

CS540 Software Design 10Lecture 5 Testing Requirements Aim: establish client’s real needs Aim: establish client’s real needs Users should be given the opportunity to review requirements document or experiment with rapid prototype (if there is one) so that their feedback and suggestions can be implemented in the final product after approval from the client (Note: Client may not be the user of the product) Users should be given the opportunity to review requirements document or experiment with rapid prototype (if there is one) so that their feedback and suggestions can be implemented in the final product after approval from the client (Note: Client may not be the user of the product) Issues must reach client Issues must reach client Requirements should be numbered for requirements traceability Requirements should be numbered for requirements traceability

CS540 Software Design 11Lecture 5 Metrics for the Requirements Phase Measure of requirements volatility – how frequently the requirements change during the requirements phase and after the requirements phase Measure of requirements volatility – how frequently the requirements change during the requirements phase and after the requirements phase How often is a screen used or not used when clients and users experiment with the prototype system How often is a screen used or not used when clients and users experiment with the prototype system

CS540 Software Design 12Lecture 5 Challenges of the Requirements Phase Employees of the client organization feel threatened by computerization Employees of the client organization feel threatened by computerization Requirements team members must be able to negotiate Requirements team members must be able to negotiate The client’s needs may have to be scaled down The client’s needs may have to be scaled down Key employees of the client organization may not have the time for essential in-depth discussions Key employees of the client organization may not have the time for essential in-depth discussions Flexibility and objectivity are essential Flexibility and objectivity are essential

CS540 Software Design 13Lecture 5 Air Gourmet Case Study Ref: (Schach 2004) pages 308 through 311 Ref: (Schach 2004) pages 308 through 311 Airlines provide ‘special dietary requirements’ food to their passengers Airlines provide ‘special dietary requirements’ food to their passengers Advantages and disadvantages Advantages and disadvantages What does Air Gourmet do? What does Air Gourmet do? What modifications does Air Gourmet want in its system? What modifications does Air Gourmet want in its system? The text suggests building a prototype. How would the interview technique work? The text suggests building a prototype. How would the interview technique work?