tailieunhanh - Lecture Software engineering (7/e): Chapter 6 – Ian Sommerville

This chapter include objectives: To introduce the concepts of user and system requirements, to describe functional and non-functional requirements, to explain how software requirements may be organised in a requirements document. | Software Requirements Objectives To introduce the concepts of user and system requirements To describe functional and non-functional requirements To explain how software requirements may be organised in a requirements document Topics covered Functional and non-functional requirements User requirements System requirements Interface specification The software requirements document Requirements engineering The process of establishing the services that the customer requires from a system and the constraints under which it operates and is developed. The requirements themselves are the descriptions of the system services and constraints that are generated during the requirements engineering process. What is a requirement? It may range from a high-level abstract statement of a service or of a system constraint to a detailed mathematical functional specification. This is inevitable as requirements may serve a dual function May be the basis for a bid for a contract - therefore must be open to | Software Requirements Objectives To introduce the concepts of user and system requirements To describe functional and non-functional requirements To explain how software requirements may be organised in a requirements document Topics covered Functional and non-functional requirements User requirements System requirements Interface specification The software requirements document Requirements engineering The process of establishing the services that the customer requires from a system and the constraints under which it operates and is developed. The requirements themselves are the descriptions of the system services and constraints that are generated during the requirements engineering process. What is a requirement? It may range from a high-level abstract statement of a service or of a system constraint to a detailed mathematical functional specification. This is inevitable as requirements may serve a dual function May be the basis for a bid for a contract - therefore must be open to interpretation; May be the basis for the contract itself - therefore must be defined in detail; Both these statements may be called requirements. Requirements abstraction (Davis) Types of requirement User requirements Statements in natural language plus diagrams of the services the system provides and its operational constraints. Written for customers. System requirements A structured document setting out detailed descriptions of the system’s functions, services and operational constraints. Defines what should be implemented so may be part of a contract between client and contractor. Definitions and specifications Requirements readers Functional and non-functional requirements Functional requirements Statements of services the system should provide, how the system should react to particular inputs and how the system should behave in particular situations. Non-functional requirements constraints on the services or functions offered by the system such as timing constraints, constraints .