1. Distinguishing between needs and requirements

Needs and requirements engineering activities are divided into two processes (standardized to ISO/IEC 15288).

• definition of stakeholder needs (steps 1 to 3); the result of the process is to present the problem and detail its expected characteristics from a user and customer point of view;

• definition of the system's technical requirements (steps 4 to 6); the result of the process is to present the problem and detail its technical characteristics from a designer's and supplier's point of view, i.e. one that enables him to design and realize a potential product, service and/or organizational system.

These processes are carried out, often by different actors, iteratively and concurrently for the same system, and recursively on the different levels of decomposition of the system...