软件工程(9v)(30+10)双语 讲义 大纲模式 - 图文

3.2.4 Functional and non-functional requirements A.1 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.

B.1 Examples of functional requirements

? The user shall be able to search either all of the initial set of databases or select a subset from

it.

? The system shall provide appropriate viewers for the user to read documents in the document

store.

? Every order shall be allocated a unique identifier (ORDER_ID) which the user shall be able

to copy to the account’s permanent storage area.

A.2 Non-functional requirements

constraints on the services or functions offered by the system such as timing constraints, constraints on the development process, standards, etc.

B.1 Non-functional classifications C.1 Product requirements

Requirements which specify that the delivered product must behave in a particular way e.g. execution speed, reliability, etc.

C.2 Organisational requirements

Requirements which are a consequence of organisational policies and procedures e.g. process standards used, implementation requirements, etc.

C.3 External requirements

Requirements which arise from factors which are external to the system and its development process e.g. interoperability requirements, legislative requirements, etc.

B.2 Non-functional requirements examples C.1 Product requirement

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4.C.8 It shall be possible for all necessary communication between the APSE(Ada Programming Support Environment) and the user to be expressed in the standard Ada character set

C.2 Organisational requirement

9.3.2 The system development process and deliverable documents shall conform to the process and deliverables defined in XYZCo-SP-STAN-95

C.3 External requirement

7.6.5 The system shall not disclose any personal information about customers apart from their name and reference number to the operators of the system

B.3 Requirements measures

Example: Experienced controllers shall be able to use all the system functions after a total of two hours training. After this training, the average number of errors made by experienced users shall not exceed two per day.

A.3 Domain requirements

Requirements that come from the application domain of the system and that reflect characteristics of that domain

B.1 examples C.1

Because of copyright restrictions, some documents must be deleted immediately on arrival. Depending on the user’s requirements, these documents will either be printed locally on the system server for manually forwarding to the user or routed to a network printer.

The deceleration of the train shall be computed as: Dtrain = Dcontrol + Dgradient where Dgradient is 9.81ms2 * compensated gradient/alpha and where the values of 9.81ms2 /alpha are known for different types of train.

C.2

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3.3 The requirements document

3.3.1 Concept

? The requirements document is the official statement of what is required of the system

developers.

? Should include both a definition of user requirements and a specification of the system

requirements.

? It is NOT a design document. As far as possible, it should set of WHAT the system should do

rather than HOW it should do it

3.3.2 Requirements document structure

1. 2. 3. 4. 5. 6. 7. 8. 9.

Introduction Glossary

User requirements definition System architecture

System requirements specification System models System evolution Appendices Index

3.3.3 Ways of writing a system requirements specification A.1 Natural language

The requirements are written using numbered sentences in natural language. Each sentence should express one requirement.

A.2 Structured natural language

The requirements are written in natural language on a standard form or template. Each field provides information about an aspect of the requirement.

B.1 Form-based specifications

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B.2 Tabular specification

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