Chapter 13 – Modeling Text-Based Requirements and Their Relationship to Design

Publisher Summary This chapter describes how text-based requirements are captured in the model and related to other model elements. A requirement specifies a capability or condition that must (or should) be satisfied, a function that a system must perform, or a performance condition a system must achieve. Requirements come from many sources, which represent multiple stakeholders. In the case of the automobile manufacturer, the requirements include government regulations for emissions control and safety as well as the direct preferences of the consumer. Regardless of the source, it is common practice to group similar requirements for a system, element, or component into a specification. The individual requirements should be expressed in clear and unambiguous terms, sufficient for the developing organization to implement a system that meets stakeholder needs. However, the classic systems engineering challenge is to ensure that requirements are consistent (not contradictory) and feasible, are validated to adequately reflect real stakeholder needs, and are verified to ensure that they are satisfied by the system design and its realization. The chapter also describes the diagrammatic representations and special notations used to represent requirements in a SysML model, which provides multiple ways for capturing requirements and their relationships in both graphical and tabular notations. A requirement diagram can be used to represent many of these relationships.