You can specify specialized requirements types by using
the subtyping features of stereotypes. Systems engineers often employ
use-case diagrams to define requirements.
The following example of these stereotypes can be
examined in the System Samples directory in the SysMLHandset project.

- <<extend>> shows
that a requirement expands or provides more detailed view of another
requirement. (See Req 4.2 and 4.1 in the example.)
- <<derive>> shows
a relationship between two requirements and supplies additional details.
A derive requirement often reflects assumptions about the implementation
of the system. (In the diagram, the arrow direction is from the derived
to the original requirement.)
- <<composite>> requirements
are the subrequirements within the overall requirements hierarchy.
With this structure a complex requirement can be decomposed into its
containing child requirements.
- <<satisfy>> relationship
identifies the system or other model element intended to satisfy or
fulfill the requirement. (In the diagram, the arrow direction is from
the satisfying to the satisfied.)
- <<verify>> shows
the relationship between a requirement and its test case. A test case
is typically expressed as an activity or interaction diagram.
- <<refine>> relationship
shows how a model element or set of elements further explains a requirement.
- <<trace>> requirement
relationship provides a general-purpose relationship between a requirement
and any other model element. The semantics of <<trace>>
do not include real constraints and, as a result, is not used with
any of the other requirements relationships listed previously.
As a systems engineers to employ use-case diagrams to define requirements,
for example, provides the following advantages:
- Naming system capabilities to add specificity to
design work
- Showing important user interactions with the system
to consider in the design
- Returning a result visible to one or more actors
- Organizing requirements by the use cases to recognize
possible design flaws early in the design process
- Assisting project planning by revealing important
relationships in the use cases