UML 2.0 Message

Call messages are always visible in diagrams; reply messages normally are not displayed. However, you can visualize the reply message.

Messages on different diagram types

Messages in communication diagrams: When you draw a message between lifelines, a generic link line displays between the lifelines and a list of messages is created under it. The link line is present as long as there is at least one message between the lifelines.

Messages in sequence diagrams: Messages in sequence diagrams have the same properties as those in communication diagrams but allow you to perform more actions. The further discussion refers mainly to the sequence diagram messages.

Properties of the messages for both types of interaction diagrams can be edited in the Object Inspector.

Properties of the message links

Call messages have the following properties:

Property	Description
Sequence number	Use this field to view and edit the sequential number of a message. When the message number changes, the message call changes respectively.
Name	Displays the link name. This field can be edited.
Qualified name	A read-only field that displays the fully-qualified name of the message.
Stereotype	Use this field to define the message stereotype. The stereotype name displays above the link.
Signature	Use this field to specify the name of an operation or signal associated with the message. Note that changing the signature of a message call results in changing the signature of the corresponding reply.
Arguments	Displays actual arguments of an operation associated with a message call. This field can be edited.
Sort	Use this field to select the type of synchronization from the drop-down list. The possible values are:asynchCall, synchCall, asynchSignal. The message link changes its appearance accordingly. There are certain limitations related to the asynchronous calls: Sometimes it is impossible to create or paste an asynchronous call because of the frame limitations. Execution specification for an asynchronous call must always be located on a lifeline.
Show reply message	Use this Boolean option to define whether to draw a dashed return arrow.
Commentary	Use this textual field to enter comments for a message link.

Reply messages have the following properties:

Property	Description
Stereotype	Use this field to define the message stereotype.
Attribute	Use this field to define an attribute to which the return value of the message will be assigned. This field can be edited.
Signature	Use this field to specify the name of an operation or signal associated with the message. Note that changing the signature of a message reply results in changing the signature of the corresponding call.
Arguments	Displays arguments of an operation associated with a message call. This field can be edited. Note that changing the list of arguments of a reply message results in changing the corresponding call.
Return value	Displays the return value of an operation associated with a message link. This field can be edited.
Sort	Use this field to select the type of synchronization from the drop-down list. The possible values are:asynchCall, synchCall, asynchSignal. The message link changes its appearance accordingly.
Commentary	Use this text field to comment the link.

Note: Such properties of the call and reply messages as arguments, attribute, qualified name, return value, signature, and sort pertain to the invocation specification. You can edit these properties in the invocation specification itself, in the call or in the reply messages. As a result, the corresponding properties of the counterpart message and the invocation specification will change accordingly. Stereotype and commentary properties are unique for the call and reply messages.