To explain what a requirement is, we could say that it translates the expression of a customer’s need into what the system or service should achieve. It’s a prerequisite for the various stages of the system design process. There are two types of requirements. First, functional requirements that translate what the system must perform. Then, non functional requirements that relate the properties that the system must have.
Each requirement must meet the following criteria:
-Be necessary for the design and operation of the system.
-To be unambiguous, to have only one possible interpretation.
-Be concise by being written in precise language, short and pleasant to read.
-Consistent: one requirement must not contradict another.
-Requirements must be grouped together and easily found by stakeholders.
-Be precisely defined with a margin of error expressed as a percentage or interval or …
-Be accessible, that is feasible with the available resources (time, money…).
-Be verifiable, that is, determined by an analysis, an inspection or a test, if the requirement is met.
For each system, it is first necessary to gather the requirements of the stakeholders. Then, you have to analyse their consistency and define (write) them in an understandable way for the users and the designers. And in order, to validate and manage them, that is, to make them evolve throughout the process.
and now on to the next subject.
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