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Week 4: Requirement Engineering Nguyễn Thị Minh Tuyền Adapted from slides of Ian Sommerville CuuDuongThanCong.com https://fb.com/tailieudientucntt Requirements Engineering £ £ £ £ £ £ What is it? Who does it? Why is it important? What are the steps? What is the work product? How do I ensure that I’ve done it right? 2 CuuDuongThanCong.com https://fb.com/tailieudientucntt Topics covered 1. 2. 3. 4. 5. 6. Functional and non-functional requirements Requirements engineering processes Requirements elicitation and analysis Requirements specification Requirements validation Requirements management 3 CuuDuongThanCong.com https://fb.com/tailieudientucntt Requirements engineering £ The process of establishing the services that a customer requires from a system and the constraints under which it operates and is developed. £ The system requirements are the descriptions of the system services and constraints that are generated during the requirements engineering process. 4 CuuDuongThanCong.com https://fb.com/tailieudientucntt What is a requirement? £ It may range from p a high-level abstract statement of a service or of a system constraint, to p a detailed mathematical functional specification. £ Requirements may serve a dual function p May be the basis for a bid for a contract - therefore must be open to interpretation; p May be the basis for the contract itself - therefore must be defined in detail; p Both these statements may be called requirements. 5 CuuDuongThanCong.com https://fb.com/tailieudientucntt Requirements abstraction (Davis) “If a company wishes to let a contract for a large software development project, it must define its needs in a sufficiently abstract way that a solution is not pre-defined. The requirements must be written so that several contractors can bid for the contract, offering, perhaps, different ways of meeting the client organization’s needs. Once a contract has been awarded, the contractor must write a system definition for the client in more detail so that the client understands and can validate what the software will do. Both of these documents may be called the requirements document for the system.” 6 CuuDuongThanCong.com https://fb.com/tailieudientucntt Types of requirement £ User requirements p Statements in natural language plus diagrams of the services the system provides and its operational constraints. p Written for customers. £ System requirements p A structured document setting out detailed descriptions of the system’s functions, services and operational constraints. p Defines what should be implemented so may be part of a contract between client and contractor. 7 CuuDuongThanCong.com https://fb.com/tailieudientucntt User and system requirements User requirement definition 1. The Mentcare system shall generate monthly management reports showing the cost of drugs prescribed by each clinic during that month. System requirements specification 1.1 On the last working day of each month, a summary of the drugs prescribed, their cost and the prescribing clinics shall be generated. 1.2 The system shall automatically generate the report for printing after 17:30 on the last working day of the month. 1.3 A report shall be created for each clinic and shall list the individual drug names, the total number of prescriptions, the number of doses prescribed and the total cost of the prescribed drugs. 1.4 If drugs are available in different dose units (e.g. 10mg, 20mg, etc.) separate reports shall be created for each dose unit. 1.5 Access to all cost reports shall be restricted to authorized users listed on a management access control list. 8 CuuDuongThanCong.com https://fb.com/tailieudientucntt Readers of different types of requirements specification User requirements Client managers System end-users Client engineers Contractor managers System architects System requirements System end-users Client engineers System architects Software developers 9 CuuDuongThanCong.com https://fb.com/tailieudientucntt System stakeholders £ Any person or organization who is affected by the system in some way and so who has a legitimate interest £ Stakeholder types p p p p End users System managers System owners External stakeholders 10 CuuDuongThanCong.com https://fb.com/tailieudientucntt