Bài giảng Công nghệ phần mềm: Chapter 3 - Nguyễn Thị Cẩm Hương

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Bài giảng Công nghệ phần mềm: Chapter 3 - Nguyễn Thị Cẩm Hương 2/25/2016 Topics covered  Functional and non-functional requirements  The software requirements document Chapter 3 – Requirements Engineering  Requirements specification  Requirements engineering processes  Requirements elicitation and analysis Lecture 1  Requirements validation  Requirements management Chapter3 Requirements engineering 1 Chapter3 Requirements engineering 2 Readers of different types of requirementsRequirements engineering specification Requirements engineering What is a requirement? Types of requirement  User requirements  System requirements Chapter3 Requirements engineering 3 Chapter3 Requirements engineering 4Functional and non-functional requirements Functional requirements  Describe functionality or system services. Functional requirements Non-functional requirements  Depend on the type of software, expected users and the type of system where the software is used. Domain requirements  Functional user requirements may be high-level statements of what the system should do.  Functional system requirements should describe the system services in detail. Chapter3 Requirements engineering 5 Chapter3 Requirements engineering 6 1 2/25/2016Requirements imprecision Requirements completeness and consistency Problems arise when requirements are not precisely  In principle, requirements should be both complete and stated. consistent. Ambiguous requirements may be interpreted in different  Complete ways by developers and users.  Consistent Consider the term ‘search’ in requirement 1  In practice, it is impossible to produce a complete and consistent requirements document.  User intention – search for a patient name across all appointments in all clinics;  Developer interpretation – search for a patient name in an individual clinic. User chooses clinic then search. Chapter3 Requirements engineering 7 Chapter3 Requirements engineering 8Non-functional requirements Types of nonfunctional requirement These define system properties and constraints Process requirements may also be specified mandating a particular IDE, programming language or development method. Non-functional requirements may be more critical than functional requirements. If these are not met, the system may be useless. Chapter3 Requirements engineering 9 Chapter3 Requirements engineering 10Non-functional requirements implementation Non-functional classifications Non-functional requirements may affect the overall  Product requirements architecture of a system rather than the individual  Organisational requirements components.  For example, to ensure that performance requirements are met,  External requirements you may have to organize the system to minimize communications between components. A single non-functional requirement, such as a security requirement, may generate a number of related functional requirements that define system services that are required.  It may also generate requirements that restrict existing requirements. Chapter3 Requirements engineering 11 Chapter3 Requirements engineering 12 2 2/25/2016 Metrics for specifying nonfunctionalGoals and req ...