Requirement Engineering

Requirements engineering is a necessity that appears in all industry standards (aeronautics, automotive, railways, nuclear, electrical equipment, space and defense). One difficulty is that no industry standard (DO 178, CENELEC, IEC 61508, etc.) provides an unambiguous, shared definition of a requirement, although there are dedicated standards such as ISO/IEC 29148. Industry standards introduce the notion of traceability (link between different elements) and the notion of level (in aeronautics we have the notion of HLR and LLR for High Level Requirement and Low Level Requirement).

This article presents the activities involved in requirements engineering and their implementation. The activities identified cover the field from the analysis of the user need to its realization. The term "realization" covers all activities from the acquisition of the requirement to the provision of the system meeting it.

Requirements engineering is the discipline of establishing and documenting requirements. The various associated activities are elucidation (translation of the word elicitation), specification, analysis, verification and validation, and management.

As a general rule, a project starts with a requirements definition phase, which aims to build a technical specification with associated performance levels. Based on the technical specification, the second phase consists of building a system that satisfies all the requirements.

It should be noted that some projects start with functional specifications or technical specifications supplied by the client (who may be a prime contractor in the case of an organization relying on several companies to build the final system). This does not mean that there has been no prior analysis of the requirements: in reality, this will have been carried out by the client, and only the technical specifications will have been supplied, which serve to control the coherence of the whole.