SYSML16 — SysML Provides Inadequate Support for Reuse of Requirements

SysML provides inadequate support for reuse of requirements. The «copy» relationship does not provide the flexibility necessary to support concepts like requirement archetypes and reusable requirement hierarchies.

SysML supports reuse in other modeling areas by distinguishing the classier (definition of the concept) from the property (use of that concept in a composition context).

• In structural modeling this is done with blocks that type part properties.
• In parametric modeling this is done with constraint blocks that type constraint properties.
  This concept has already been extended in SysML to include activity modeling: activities (classifiers) called by call behavior actions, and depicting these called behavior actions as adjunct properties on a block definition diagram.

In all three cases, the vehicle for reuse is a classifier that types or is called by a property of another classifier. It is appropriate to extend this approach to requirements, thus supporting requirement archetypes as classifiers, and requirements as properties of classifiers.

• Requirement hierarchy can then follow the standard composition relationship, rather than the current containment relationship.
• Requirements as properties are contextualized by the classifier owning them, yet inherit characteristics of the requirement archetype classifier typing them.

SysML Provides Inadequate Support for Reuse of Requirements

This is addressed in SysML 1.5 with property based requirements by allowing Blocks for requirements.
This allows to contextualize the requirement and therefore re-use the requirement.

See E.8.4 An Example Property Based Requirement based on Block