SYSML11 — SysML: Use Cases

The text in 14.1 should briefly discuss that for System Engineers, run-time optionality is not the typical distinction for indentifying extensions. If we wanted to draw a flow chart, we would use an activity diagram.

It is usually more relevant to identify as extensions those use cases that not are needed to reach the goal of the base use case. This allows the System Engineers to use the dependency graph among the use cases to help determine production/test/delivery order.

This also makes it clear to the reviewer which features are considered optional and which are not. At the SE level, this is more important that than flagging those features that sometimes invoked and sometimes not invoked.

Please clarify with this use at the SE level

Instead of a long discussion on the differences between SW and SE perspectives
on use cases, we add some words to clarify the SE goal/requirement-oriented
perspective, trying to avoided use of UCDs as flow charts. This approach leaves
open the possibility of compatibility with SW approaches.
In addition, a minor grammatical error is fixed.
Revised Text: