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参考定義 anchor.png

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IEEE std 830-1998 (Unambiguous) anchor.png

An SRS is unambiguous if, and only if, every requirement stated therein has only one interpretation. As a minimum, this requires that each characteristic of the final product be described using a single unique term.

In cases where a term used in a particular context could have multiple meanings, the term should be included in a glossary where its meaning is made more specific.

An SRS is an important part of the requirements process of the software life cycle and is used in design, implementation, project monitoring, verification and validation, and in training as described in IEEE Std 1074-1997. The SRS should be unambiguous both to those who create it and to those who use it. However, these groups often do not have the same background and therefore do not tend to describe software requirements the same way. Representations that improve the requirements specification for the developer may be counterproductive in that they diminish understanding to the user and vice versa.

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Requirements are often written in natural language (e.g., English). Natural language is inherently ambiguous. A natural language SRS should be reviewed by an independent party to identify ambiguous use of language so that it can be corrected.

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One way to avoid the ambiguity inherent in natural language is to write the SRS in a particular requirements specification language. Its language processors automatically detect many lexical, syntactic, and semantic errors.

One disadvantage in the use of such languages is the length of time required to learn them. Also, many nontechnical users find them unintelligible. Moreover, these languages tend to be better at expressing certain types of requirements and addressing certain types of systems. Thus, they may influence the requirements insubtle ways.

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In general, requirements methods and languages and the tools that support them fall into three general categories-object, process, and behavioral. Object-oriented approaches organize the requirements in terms of real-world objects, their attributes, and the services performed by those objects. Process-based approaches organize the requirements into hierarchies of functions that communicate via data ßows. Behavioral approaches describe external behavior of the system in terms of some abstract notion (such as predicate calculus), mathematical functions, or state machines.

The degree to which such tools and methods may be useful in preparing an SRS depends upon the size and complexity of the program. No attempt is made here to describe or endorse any particular tool.

When using any of these approaches it is best to retain the natural language descriptions. That way, customers unfamiliar with the notations can still understand the SRS.

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IEEE std 830-1998 和訳例 anchor.png

SRSのすべての要求の意味が一意に識別されること
(月刊「ビジネスコミュニケーション」((株)ビジネスコミュニケーション社)の「要求工学」第3回「要求仕様」による)


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Last-modified: 2013-07-22 (Mon) 04:20:19 (JST) (2100d) by ShioyaAtsuko