The Sequence Diagram (sd) is used to represent the interaction between structural elements (Blocks and Actors) of a system, as a sequence of message exchanges between the Blocks/Actors:
Sequence Diagrams are composed of Block/Actor Lifelines and the Message Events that are exchanged between the Lifelines. The Lifeline symbol has a trailing dashed line that represents the object's timeline where the time flows top to bottom.
A message is shown on an sd as a line with different arrowheads and annotations depending on the type of message (synchronous or asynchronous). The logic needed to produce and/or consume the identified messages can be optionally shown on the sd as Execution Specifications.
An example sd is:
The symbols available in sds are:
The symbols along with their default stereotypes, referenced elements, stereotype frames and cross reference link attributes are: