TABLE OF CONTENTS This chapter describes how text-based requirements are captured in the model and related to other model elements. This chapter also describes the diagrammatic representations and special notations used to represent requirements and other cross-cutting relationships, such as allocations, in a SysML model.
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. Sometimes requirements are provided directly by the person or organization paying for the system, such as a customer who hires a contractor to build his or her house. Other times, requirements are generated by the organization that is developing the system, such as an automobile manufacturer that must determine the consumer preferences for its product. The source of requirements often reflects multiple stakeholders. In the case of the automobile manufacturer, the requirements will 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 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, have been validated to adequately reflect real stakeholder needs, and have been verified to ensure that they are satisfied by the system design.
Requirements management...
