In UML, generalization as a way of factoring out commonality
between use cases. In other words, it provides a means to derive one
use case from another. Generalizations are allowed between use cases
and actors.
Procedure
- Click the Generalization button
,
and then click the derived use case, for example, use case B.
- Move the cursor to the closest edge of the
super-use case, for example, use case A, and click once.
- Create a generalization from, for example, use case C to
use case A. Notice that by default, the lines appear in a tree style.
For more information and an example of the tree line shape,
see Creating inheritances in object model diagrams.
If
you add another use case to your diagram, for example, use case D,
you can add it to the tree structure by clicking the Generalization
arrow from use case D onto use case A or onto a line on that tree.
Note: If
the line style for generalizations is not set to display in a tree
style by default, to apply this line shape to two or more generalization
lines pointing to the same target, select one of the generalization
lines (for example, from use case B to use case A) and select . You can also do this by targeting a generalization
line to another generalization line that points to the same target.
For example, if you have a generalization line from use case B to
use case A, you can create a tree structure by touching the BA line
with the generalization line from use case C.
Results
For use case diagrams, the line shape for generalizations
is set by the UseCaseGe::Inheritance::line_style property.