About Sequence Diagram View

A sequence diagram view is an interaction diagram that shows the interactions between the different entities of a system. A sequence diagram view is based on a functional or logical structure.

This page discusses:

Sequence Diagram View Structure

A sequence diagram view is always created in a sheet. This sheet can be attached to a function or a logical component.



Elements of a Sequence Diagram View

In a sequence diagram view, you can insert different elements.

Actor and Lifeline

An actor is a basic component of a system. It is associated to a lifeline.

In a sequence diagram view, it represents a function or a logical component.

An actor can interact with other actors.

Activation

An activation is an execution specification. It indicates that the actor answers to messages.

Message

A message is a communication link or a signal transmitted from an actor to another.

A message or multiple messages can be inserted between two actors displayed in a sequence diagram view.

When you create a message, a message point is created to connect the following objects:

  • Messages and lifelines
  • Messages and activations
  • Messages and interaction uses

There are three types of messages you can define when you create a message:

  • Synchronous
  • Asynchronous
  • Return

A message can be defined with several variables:

  • Duration constraint
  • Duration observation
  • Time observation
  • Time constrain
Note: For more information about message variables, see About Message Variables

Interaction Use

An interaction use can be inserted in a sequence diagram view. It represents another sequence diagram in the current sequence diagram view.

An interaction use can be associated to message points and linked to one or several lifelines.

Block and Guard

A block can be inserted in a sequence diagram view to group messages and interaction use elements. Multiple blocks can be grouped in a guard.

A guard can be inserted in a sequence diagram view to group multiple blocks and apply them a condition. There are five conditions:

  • Alternative
  • Option
  • Loop
  • Parallel
  • Break