In sequence diagrams and communication diagrams, you can show operation
signatures or message signatures of individual messages to visually represent
communication in interactions.
You must have a sequence diagram or communication diagram open that
contains messages.
To show an operation or message signature, in the diagram editor,
right-click a message; then click .
The operation signature or message signature is displayed in the name
compartment.
Note: If the message has no arguments, the operation
signature of the message is displayed. If the global preference Show
Operation signatures instead of Message signatures is selected,
the operation signature of the message is always displayed.