2 Requirements Documentation Once elicited the next step is to document the

2 requirements documentation once elicited the next

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2. Requirements Documentation. Once elicited, the next step is to document the requirements in a Software Requirements Specification ( SRS ). Figure 7.13 gives an outline for an SRS based on IEEE Standard 830-1998. A SRS for a patient management system is 14 pages long, but they are often hundreds of pages. Table of Contents 1. Introduction 1.1 Purpose 1.2 Scope 1.3 Definitions, acronyms, and abbreviations 1.4 References 1.5 Overview 2. Overall description 2.1 Product perspective 2.2 Product functions 2.3 User characteristics 2.4 Constraints 2.5 Assumptions and dependencies 3. Specific requirements 3.1 External interface requirements
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3.1.1 User interfaces 3.1.2 Hardware interfaces 3.1.3 Software interfaces 3.1.4 Communication interfaces 3.2 System features 3.2.1 System feature 1 Introduction/purpose of feature Stimulus/response sequence Associated function requirements Functional requirement 1 . . . Functional requirement n 3.2.2 System feature 2 . . . 3.2.m System feature m 3.3 Performance requirements 3.4 Design constraints 3.5 Software system attributes 3.6 Other requirements Figure 7.13: A table of contents for the IEEE Standard 830-1998 recommended practice for Software Requirements Specifications. We show Section 3 organized by feature, but the standard offers many others ways to organize Section 3: by mode, user class, object, stimulus, functional hierarchy, or even mixing multiple organizations. Part of the process is to check the SRS for: Validity–are all these requirements really necessary? Consistency–do requirements conflict? Completeness–are all requirements and constraints included? Feasibility–can the requirements really be implemented? Techniques to test for these four characteristics include having stakeholders—developers, customers, testers, and so on—proof-read the document, trying to build a prototype that includes the basic features, and generating test cases that check the requirements. A project may find it useful to have two types of SRS: a high-level SRS that is for management and marketing and a detailed SRS for the project development team. The former is presumably a subset of the latter. For example, the high-level SRS might leave out the functional requirements that correspond to in Figure 7.13 . ELABORATION: Formal specification languages Formal specification languages such as Alloy or Z allow the project manager to write executable requirements, which makes it easier to validate the implementation. Not surprisingly, the cost is both a more difficult document to write and usually a much longer requirements document to read. The advantage is both precision in the specification and the potential to automatically generate tests
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cases or even use formal methods for verification of correctness (see Section 8.9 ). 3. Cost Estimation. The project manager then decomposes the SRS into the tasks to implement it, and then estimates the number of weeks to complete each task. The advice is to decompose no finer than one week. Just as a user story with more than seven points should be divided into smaller user stories, any task with an estimate of more than eight weeks should be further divided into smaller tasks.
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  • Spring '19
  • Dr.Marcos

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