Interaction operators, which are included in UML 2.0, are
used to group related elements in a sequence diagram. This includes
the option of defining specific conditions under which each group
of elements is to occur.
About this task
Each interaction operator has a type, which
determines its behavior, for example Opt, Par, or Loop.
In addition, interaction operators can include a guard
to specify specific conditions under which the path is to take.
Interaction operators can be nested where necessary.
To add an interaction operator to a diagram: