Communication diagrams

Definition

Communication diagrams show how different nodes cooperate, focusing on the architecture of the internal structure and how this corresponds with the message passing. The sequencing of messages is given through the sequence numbering scheme.

Communication diagrams (an example is shown below) are created in communication interactions.

An example of a communication diagram

Communication nodes

A communication node represents an object in the communication interaction. It can be a representation of an instance.

To create a communication node in a communication diagram, click on the "Create a communication node" icon and then in the diagram background. A new communication node is inserted and given a default name that you can edit.

This new communication node doesn’t yet represent any element of the model, but you can then use the edition dialog box to make it represent an instance.

Communication channels

Communication channels are the channels used by communication nodes to exchange communication messages.

To create a communication channel, simply click on the "Create a communication channel" icon and then on the two communication nodes that are to be linked by this channel.

Communication messages

Messages are used in communication diagrams to express the flow of communication between the different elements of the diagram.

A communication message can be a representation of an invoked operation or a sent message. This can be set in the communication message's edition dialog box.

To create a communication message, click on the "Create a communication message" icon and then click on the communication channel through which this message will be sent. From the two nodes linked by the selected channel, the communication node nearest the mouse cursor at the time of the click will be considered as being the sender of the newly created communication message, and thus the message will be added to the list of messages sent by this node through this channel. To help understand which node will be chosen as the sender, the mouse cursor will take the form of an arrow when hovering over a communication channel, with the direction of the arrow indicating the direction of the message through the channel.

Note: A communication message is graphically represented by a label followed by a small arrow icon showing the direction of the message.