Activations (OOM)

Activations are optional symbols that represent the time required for an action to be performed. They are created on the lifeline of an object. They are purely symbols and do not have property sheets.

An activation can be created in the following diagrams:

In a communication diagram, messages that are passed during the period represented by an activation are given sub-numbers. Thus an activation created by message 1, may give rise to messages 1.1 and 1.2.

You can attach or detach a message to an activation. You can also move, resize, and cause the activation to overlap other activations.

• Creating an Activation
  You can create an activation when you create a Procedure Call message or afterwards for any type of message. A Procedure Call generally starts an activation, that is why the message is automatically attached to an activation.
• Attaching a Message to an Activation
  A message is attached to an activation when its begin or endpoint is on the activation symbol and not on the object lifeline. Attachment symbols appear at the endpoints of the message arrow (if attachment symbols are not displayed, select Tools > Display Preferences, and select the Activation Attachment display preference in the Message category).
• Detaching a Message from an Activation
  You can detach a message from an activation by dragging the message outside the activation, while holding the Ctrl key down.
• Overlapping Activations
  An activation can overlap other existing activations.
• Moving an Activation
  If you move an activation with a message attached to it, the message does not move. Thus, it is possible to move the activation up and down until its top or bottom reaches the message level.:
• Resizing an Activation
  You may want to resize an activation by pulling the top or bottom of the activation symbol. This will resize the activation vertically.