1. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 1 Software Engineering: A Practitioner’s Approach, 6/e Chapter 7 Requirements Engineering Software Engineering: A Practitioner’s Approach, 6/e Chapter 7 Requirements Engineering copyright © 1996, 2001, 2005 R.S. Pressman & Associates, Inc. For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited.

2. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 2 Requirements Engineering Stages: Stages: Inception Inception Elicitation Elicitation Elaboration Elaboration Negotiation Negotiation Specification Specification Validation Validation Management Management

3. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 3 Requirements Engineering Inception—ask a set of questions that establish … Inception—ask a set of questions that establish … basic understanding of the problem basic understanding of the problem the people who want a solution the people who want a solution the nature of the solution that is desired, and the nature of the solution that is desired, and the effectiveness of preliminary communication and collaboration between the customer and the developer the effectiveness of preliminary communication and collaboration between the customer and the developer Elicitation—elicit requirements from all stakeholders Elicitation—elicit requirements from all stakeholders address problems of scope address problems of scope address problems of understanding address problems of understanding customers not sure about what is needed, skip “obvious” issues, have difficulty communicating with the software engineer, have poor grasp of problem domain customers not sure about what is needed, skip “obvious” issues, have difficulty communicating with the software engineer, have poor grasp of problem domain address problems of volatility address problems of volatility

4. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 4 Requirements Engineering Elaboration—create an analysis model that identifies data, function, features, constraints and behavioral requirements Elaboration—create an analysis model that identifies data, function, features, constraints and behavioral requirements Negotiation—agree on a deliverable system that is realistic for developers and customers Negotiation—agree on a deliverable system that is realistic for developers and customers rank requirements by priority (conflicts arise here …) rank requirements by priority (conflicts arise here …) identify and analyze risks assoc. with each requirement identify and analyze risks assoc. with each requirement “guestimate” efforts needed to implement each requirement “guestimate” efforts needed to implement each requirement eliminate, combine and / or modify requirements to make project realistic eliminate, combine and / or modify requirements to make project realistic

5. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 5 Requirements Engineering Specification—can be any one (or more) of the following: Specification—can be any one (or more) of the following: A written document A written document A set of models A set of models A formal mathematical model A formal mathematical model A collection of user scenarios (use-cases) A collection of user scenarios (use-cases) A prototype A prototype Validation—a review mechanism that looks for: Validation—a review mechanism that looks for: errors in content or interpretation errors in content or interpretation areas where clarification may be required areas where clarification may be required missing information missing information inconsistencies (a major problem when large products or systems are engineered) inconsistencies (a major problem when large products or systems are engineered) conflicting or unrealistic (unachievable) requirements conflicting or unrealistic (unachievable) requirements

6. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 6 Requirements Engineering Requirements management involves managing change: Requirements management involves managing change: Feature traceability: how requirements relate to observable system/product features Feature traceability: how requirements relate to observable system/product features Source traceability: identifies source of each requirement Source traceability: identifies source of each requirement Dependency traceability: how requirements are related to each other Dependency traceability: how requirements are related to each other Subsystem traceability: categorizes requirements by the subsystem(s) they govern Subsystem traceability: categorizes requirements by the subsystem(s) they govern Interface traceability: how requirements relate to both external and internal system interfaces Interface traceability: how requirements relate to both external and internal system interfaces

7. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 7 Inception Identify stakeholders Identify stakeholders “whom else do you think I should talk to?” “whom else do you think I should talk to?” Recognize multiple points of view Recognize multiple points of view Work toward collaboration Work toward collaboration The first questions: The first questions: Who is behind the request for this work? Who is behind the request for this work? Who will use the solution? Who will use the solution? What will be the economic benefit of a successful solution? What will be the economic benefit of a successful solution? Is there another source for the solution that you need? Is there another source for the solution that you need?

8. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 8 Inception The subsequent questions: The subsequent questions: What constitutes a “good” output from the system? What constitutes a “good” output from the system? What problem(s) does this solution address? What problem(s) does this solution address? What is the intended business environment for this solution? What is the intended business environment for this solution? What performance issues or constraints should affecting my approach to the solution What performance issues or constraints should affecting my approach to the solution

9. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 9 Inception The final questions: The final questions: Are your answers official? Are your answers official? Are my questions relevant? Are my questions relevant? Am I asking too many questions? Am I asking too many questions? Can anyone else provide additional info? Can anyone else provide additional info? Should I be asking anything else? Should I be asking anything else?

10. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 10 Eliciting Requirements Meetings are conducted and attended by both software engineers and customers Meetings are conducted and attended by both software engineers and customers Rules for preparation and participation are established Rules for preparation and participation are established An agenda is suggested An agenda is suggested A "facilitator" (can be a customer, a developer, or an outsider) controls the meeting A "facilitator" (can be a customer, a developer, or an outsider) controls the meeting A "definition mechanism" (can be work sheets, flip charts, or wall stickers or an electronic bulletin board, chat room or virtual forum) is used A "definition mechanism" (can be work sheets, flip charts, or wall stickers or an electronic bulletin board, chat room or virtual forum) is used The goal is The goal is to identify the problem to identify the problem propose elements of the solution propose elements of the solution negotiate different approaches, and negotiate different approaches, and specify a preliminary set of solution requirements specify a preliminary set of solution requirements

11. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 11

12. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 12 Quality Function Deployment A technique of translating customer needs into technical system requirements: A technique of translating customer needs into technical system requirements: Normal requirements: reflect stated customer goals and objectives Normal requirements: reflect stated customer goals and objectives Expected requirements: implicit to the product or system; their absence will cause significant customer dissatisfaction Expected requirements: implicit to the product or system; their absence will cause significant customer dissatisfaction Exciting requirements: featured going beyond customer expectations, causing customer euphoria (;-) Exciting requirements: featured going beyond customer expectations, causing customer euphoria (;-)

13. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 13 Quality Function Deployment Function deployment determines the “value” (as perceived by the customer) of each function required of the system Function deployment determines the “value” (as perceived by the customer) of each function required of the system Information deployment identifies data objects and events Information deployment identifies data objects and events Task deployment examines the behavior of the system Task deployment examines the behavior of the system Value analysis determines the relative priority of requirements Value analysis determines the relative priority of requirements

14. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 14 Elicitation Work Products A statement of need and feasibility. A statement of need and feasibility. A bounded statement of scope for the system or product. A bounded statement of scope for the system or product. A list of customers, users, and other stakeholders who participated in requirements elicitation A list of customers, users, and other stakeholders who participated in requirements elicitation A description of the system’s technical environment. A description of the system’s technical environment. A list of requirements (preferably organized by function) and the domain constraints that apply to each. A list of requirements (preferably organized by function) and the domain constraints that apply to each. A set of usage scenarios that provide insight into the use of the system or product under different operating conditions. A set of usage scenarios that provide insight into the use of the system or product under different operating conditions. Any prototypesdeveloped to better define requirements Any prototypes developed to better define requirements.

15. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 15Use-Cases A collection of user scenarios that describe the thread of usage of a system A collection of user scenarios that describe the thread of usage of a system Each scenario is described from the point-of-view of an “actor”—a person or device that interacts with the software in some way Each scenario is described from the point-of-view of an “actor”—a person or device that interacts with the software in some way Each scenario answers the following questions: Each scenario answers the following questions: Who is the primary actor, the secondary actor (s)? Who is the primary actor, the secondary actor (s)? What are the actor’s goals? What are the actor’s goals? What preconditions should exist before the story begins? What preconditions should exist before the story begins? What main tasks or functions are performed by the actor? What main tasks or functions are performed by the actor? What extensions might be considered as the story is described? What extensions might be considered as the story is described? What variations in the actor’s interaction are possible? What variations in the actor’s interaction are possible? What system information will the actor acquire, produce, or change? What system information will the actor acquire, produce, or change? Will the actor have to inform the system about changes in the external environment? Will the actor have to inform the system about changes in the external environment? What information does the actor desire from the system? What information does the actor desire from the system? Does the actor wish to be informed about unexpected changes? Does the actor wish to be informed about unexpected changes?

16. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 16 Use-Case Diagram

17. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 17 Building the Analysis Model Intent: to provide a description of the required informational, functional and behavioral domains of the computer-based system Intent: to provide a description of the required informational, functional and behavioral domains of the computer-based system The model changes dynamically as the system engineers learn more about the system The model changes dynamically as the system engineers learn more about the system Is a series of time-ordered snapshots of requirements Is a series of time-ordered snapshots of requirements

18. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 18 Building the Analysis Model Elements of the analysis model Elements of the analysis model Scenario-based elements Scenario-based elements Functional—processing narratives for software functions Functional—processing narratives for software functions Use-case—descriptions of the interaction between an “actor” and the system Use-case—descriptions of the interaction between an “actor” and the system Class-based elements Class-based elements Implied by scenarios Implied by scenarios Behavioral elements Behavioral elements State diagram State diagram Flow-oriented elements Flow-oriented elements Data flow diagram Data flow diagram

19. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 19 Class Diagram From the SafeHome system …

20. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 20 State Diagram

21. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 21 Analysis Patterns Pattern name: A descriptor that captures the essence of the pattern. Intent: Describes what the pattern accomplishes or represents Motivation: A scenario that illustrates how the pattern can be used to address the problem. Forces and context: A description of external issues (forces) that can affect how the pattern is used and also the external issues that will be resolved when the pattern is applied. Solution: A description of how the pattern is applied to solve the problem with an emphasis on structural and behavioral issues. Consequences: Addresses what happens when the pattern is applied and what trade- offs exist during its application. Design: Discusses how the analysis pattern can be achieved through the use of known design patterns. Known uses: Examples of uses within actual systems. Related patterns: On e or more analysis patterns that are related to the named pattern because (1) it is commonly used with the named pattern; (2) it is structurally similar to the named pattern; (3) it is a variation of the named pattern.

22. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 22 Negotiating Requirements Identify the key stakeholders Identify the key stakeholders These are the people who will be involved in the negotiation These are the people who will be involved in the negotiation Determine each of the stakeholders “win conditions” Determine each of the stakeholders “win conditions” Win conditions are not always obvious Win conditions are not always obvious Negotiate Negotiate Work toward a set of requirements that lead to “win-win” Work toward a set of requirements that lead to “win-win”

23. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 23 Validating Requirements Checking for Consistency, Omissions, Ambiguity Is each requirement consistent with the overall objective for the system/product? Is each requirement consistent with the overall objective for the system/product? Have all requirements been specified at the proper level of abstraction? That is, do some requirements provide a level of technical detail that is inappropriate at this stage? Have all requirements been specified at the proper level of abstraction? That is, do some requirements provide a level of technical detail that is inappropriate at this stage? Is the requirement really necessary or does it represent an add-on feature that may not be essential to the objective of the system? Is the requirement really necessary or does it represent an add-on feature that may not be essential to the objective of the system? Is each requirement bounded and unambiguous? Is each requirement bounded and unambiguous? Does each requirement have attribution? That is, is a source (generally, a specific individual) noted for each requirement? Does each requirement have attribution? That is, is a source (generally, a specific individual) noted for each requirement? Do any requirements conflict with other requirements? Do any requirements conflict with other requirements?

24. These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 24 Validating Requirements Is each requirement achievable in the technical environment that will house the system or product? Is each requirement achievable in the technical environment that will house the system or product? Is each requirement testable, once implemented? Is each requirement testable, once implemented? Does the requirements model properly reflect the information, function and behavior of the system to be built. Does the requirements model properly reflect the information, function and behavior of the system to be built. Has the requirements model been “partitioned” in a way that exposes progressively more detailed information about the system. Has the requirements model been “partitioned” in a way that exposes progressively more detailed information about the system. Have requirements patterns been used to simplify the requirements model. Have all patterns been properly validated? Are all patterns consistent with customer requirements? Have requirements patterns been used to simplify the requirements model. Have all patterns been properly validated? Are all patterns consistent with customer requirements?