Correctness of the specification can only be verified

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correctness of the specification can only be verified if the criterion of understandability is met. Consistent: [IEEE Std. 830-1998] Requirements must be consistent with regard to all other requirements, i.e., the requirements must not contradict one another, regardless of their level of detail or documenta- tion type. In addition, a requirement must be formulated in a way that allows for consistency with itself, i.e., the requirement may not contra- dict itself. Verifiable: [IEEE Std. 830-1998 ] A requirement must be described in a way that allows for verification. That means that tests or measurements can be carried out that provide evidence of the functionality demanded by the requirement. Realizable: It must be possible to implement each requirement given the organizational, legal, technical, or financial constraints. This means that a member of the development team ought to be involved in rating the goals and requirements so that he can show the technical limits of the implementation of a particular requirement. In addition, the costs for the implementation must be incorporated into the rating. Occa- sionally, stakeholders withdraw a requirement if the costs for its reali- zation become apparent. Traceable: [IEEE Std. 830-1998] A requirement is traceable if its origin as well as realization and its relation to other documents can be retraced. This can be done by means of unique requirement identifiers.
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4.7 Glossary 45 Using these unique identifiers, requirements that are derived from other requirements on a different level of the specification can be con- nected. For example, a system goal can be traced through all levels of abstraction, from design to implementation and test. Details can be found in section 8.4. Complete: [IEEE Std. 830-1998] Each individual requirement must completely describe the functionality it specifies. Requirements that are yet incomplete must be specially marked, for example by inserting “tbd” (“to be determined”) into the respective text field or by setting a corresponding status. These markings can then be systematically searched for and missing information can be amended accordingly. Understandability: Requirements must be comprehensible to each stakeholder. Therefore, the type of requirements documentation (see section 4.2 ) can vary significantly, depending on the development phase (and therefore, depending on the involved staff). In require- ments engineering, it is important to strictly define the terms used. Fundamental principles of understandability Along with quality criteria for requirements, there are two fundamental rules that enhance the readability of requirements: Short sentences and short paragraphs: As human short-term memory is very limited, circumstances that belong together should be described in no more than seven sentences.
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