In particular, it does not include calculation
resources, and no data is exchanged, but there may be an exchange of forces, for
example.
Similar to an external system, a mechanical system is denoted as a box with an
additional tool symbol ( Figure 2.18 ).
FIGURE 2-15
The notation for boundary systems.
bdd [package] SysML book [notation for interface systems]
Interface system
FIGURE 2-16
An environmental effect ??? temperature. ???
bdd [package] On-board computer context
[environmental effect]
Temperature
?«system?»
On-board computer
51
You should be careful not to defi ne too many categories, though. Here too, less is
more. Think carefully about the goals you want to achieve with a new category before
you introduce it. Will it make the diagrams easier to understand and improve the communication?
Will it help winning more information or focus on an important fact?
How would you model the actors if you were NOT to introduce a new category?
The system context diagram may make a trivial impression. In practice, however,
searching for actors can lead to diffi cult discussions.
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