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Requirements Analysis

Requirements Analysis. CS 414 – Software Engineering I Donald J. Bagert Rose-Hulman Institute of Technology January 7, 2003. Outline. Engineering of Requirements Requirements Elicitation Requirements Analysis Specification Screen Prototyping Review, Negotiation and Agreement

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Requirements Analysis

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  1. Requirements Analysis CS 414 – Software Engineering I Donald J. Bagert Rose-Hulman Institute of Technology January 7, 2003

  2. Outline • Engineering of Requirements • Requirements Elicitation • Requirements Analysis • Specification • Screen Prototyping • Review, Negotiation and Agreement • Requirements Management • Validation Test Planning • Summary CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  3. Engineering of Requirements • The development and management of requirements is something that is much the same across disciplines e.g. • The entire system must always be taken into account • The client frequently supplies vague, incomplete and sometimes contradictory information • The client often has unrealistic expectations • Requirements must be specified and subsequently matched to design • The requirements may change due for a variety of reasons, and must be managed throughout the project process • This process is called “requirements engineering” CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  4. Requirements Elicitation • Elicitation is determining the system requirements through interaction with the client and other project stakeholders • This is a non-trivial task, since the information supplied is often • incomplete • inconsistent • ambiguous CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  5. Requirements Elicitation(continued) • Primary goals of elicitation: • Determining system feasibility • Determining the technical environment of the system • Creating a list of desired functions of the system • Determining any constraints on the system (“non-functional requirements”) • Compiling a list of scenarios that will occur during use of the system CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  6. Requirements Analysis • Organizes the elicitation results • Categorizes and prioritizes the system requirements • Determines if the requirements are complete, consistent and unambiguous CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  7. Specification • The Requirements Specification Document (RSD) is the end result of the analysis process • Major components of the specification include: • System model • User characteristics • Requirements • Functions • Constraints • Use Cases • Tracing (cross-referencing) of requirements and use cases to client requirements CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  8. Specification (continued) • Types of System Models • Data-flow diagrams • Control-flow diagrams (system behavior) • Entity-relationship diagrams • High-level software architecture CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  9. Specification (continued) • Use cases • Creating using the scenarios determined during elicitation • Sections • Overview • Preconditions • Scenario Details and Context • Postconditions • Exception Handling CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  10. Specification (continued) • The Requirements Specification for this course includes a section on the scope of the project since there is a time-limit involved CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  11. Screen Prototyping • Screen Prototypes: • Should be submitted to the client in addition to the Requirements Specification • Gives the client a better idea of what is being proposed • Can be quickly created using languages such as Visual Basic and Tcl/Tk CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  12. Review, Negotiation and Agreement • Both the vendor and the client should review the Requirements Specification Document • Internal review can be in the form of an inspection, which should be done (if time permits) before submission to the client CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  13. Review, Negotiation and Agreement (continued) • Some of the questions to be asked: • Are all sections of the template included? • Has a clear, brief summary is given of the client's needs supplied? • Is the current client system diagram accurate? • Are the user characteristics are given clearly and completely? • Are all requirements are well organized, clear, understandable, unambiguous, consistent, non-conflicting, necessary, and non-redundant? • Are all diagrams in the requirements use standard notation and are also clear and complete? • Are the requirements are appropriately numbered and cross-referenced making it easy to ensure all requirements have been met in the project? CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  14. Review, Negotiation and Agreement (continued) • The client should then review the Requirements Specification, screen prototypes, Project Plan and budget • The client and vendor then negotiate a formal written agreement, which includes: • Functionality to be included in the delivered software • Artifacts to be delivered • Schedule for delivery of artifacts • Amount to be paid by the client to the vendor, and schedule of payments CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  15. Requirements Management • Changes to requirements after the formal agreement is reached • Traceability of RSD elements to the Design Document and (indirectly) to other artifacts CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  16. Validation Test Planning • Validation answers the question “Have we got the right product?” • That is, validation of an artifact is the process of determining whether that artifact meets the customer requirements • A Validation Test Plan defines the set of tests to be done to validate the software • Validation test cases can be largely created from the RSD use cases, and should always be from the user point-of-view • Should be created as soon as possible after the formal agreement is reached (to avoid bias from the design) • Modified as necessary as part of requirements management • Implemented as the last step of testing by the project team CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  17. Summary • Requirements engineering refers to the development and management of requirements across disciplines • The client frequently supplies vague, incomplete and sometimes contradictory information, and often has unrealistic expectations • Requirements elicitation is the process of determining the system requirements through interaction with the client and other project stakeholders • Analysis organizes the elicitation results and categorizes and prioritizes the system requirements CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  18. Summary (continued) • The Requirements Specification Document is the end result of the analysis process • The Requirements Specification, screen prototypes, Project Plan and budget should be submitted to the client for review • The client and vendor then negotiate a formal written agreement CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

  19. Summary (continued) • Requirements management is need to handle changes to requirements after the formal agreement is reached, and to the trace requirements to design and other artifacts • The Validation Test Plan is created from the requirements in order to eventually test the software from the user’s point-of-view CS 414 Software Engineering I - Requirements Analysis - January 7, 2003

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