Drawing sequence diagrams

A sequence diagram is a kind of UML diagram that is used primarily to show the interactions between objects that are represented as lifelines in a sequential order.

Creating sequence diagram

Perform the steps below to create a UML sequence diagram Visual Paradigm uml diagram tools.

  1. Select Diagram > New from the application toolbar.
  2. In the New Diagram window, select Sequence Diagram.
  3. Click Next.
  4. Enter the diagram name and description. The Location field enables you to select a model to store the diagram.
  5. Click OK.

Creating actor

To create actor, click Actor on the diagram toolbar and then click on the diagram.

Create actor
Create actor

Creating lifeline

To create lifeline, you can click LifeLine on the diagram toolbar and then click on the diagram.

Alternatively, a much quicker and more efficient way is to use Resource Catalog:

  1. Move your mouse pointer over the source lifeline.
  2. Press on the Resource Catalog button and drag it out.
    Using Resource Catalog
    Using Resource Catalog
  3. Release the mouse button at the place where you want the lifeline to be created.
  4. Select Message -> LifeLine from Resource Catalog.
    To create a lifeline
    To create a lifeline
  5. A new lifeline will be created and connected to the actor/lifeline with a message. Enter its name and press Enter to confirm editing.
    Lifeline created
    Lifeline created

Auto extending activation

When create message between lifelines/actors, activation will be automatically extended.

Auto extending activation
Auto extending activation

Using sweeper and magnet to manage sequence diagram

Sweeper helps you to move shapes aside to make room for new shapes or connectors. To use sweeper, click the Selector on the toolbar, then select Sweeper.

sweeper
sweeper

Click on empty space of the diagram and drag towards top, right, bottom or left. Shapes affected will be swept to the direction you dragged.

The picture below shows the actor Inspector Assistant is being swept towards right, thus new room is made for new lifelines.

Sweep towards right
Sweep towards right

The picture below shows the message specify visit time is being swept downwards, thus new room is made for new messages.

Sweep downwards
Sweep downwards

You can also use magnet to pull shapes together. To use magnet, click the Selector on the toolbar, then select Magnet.


Magnet

Click on empty space of the diagram and drag towards top, right, bottom or left. Shapes affected will be pulled to the direction you dragged.

The picture below shows when drag the magnet upwards, shapes below dragged position are pulled upwards.

Pull shapes upwards using magnet
Pull shapes upwards using magnet

Creating combined fragment for messages

To create combined fragment to cover messages, select the messages, right-click on the selection and select Create Combined Fragment and then select a combined fragment type (e.g. loop) from the popup menu.

Create combined fragment for messages
Create combined fragment for messages

A combined fragment of selected type will be created to cover the messages.

Combined fragment created
Combined fragment created

Adding/removing covered lifelines

After you've created a combined fragment on the messages, you can add or remove the covered lifelines.

  1. Move the mouse over the combined fragment and select Add/Remove Covered Lifeline... from the pop-up menu.
    Add/Remove covered lifelines
    Add/Remove covered lifelines
  2. In the Add/Remove Covered Lifelines window, check the lifeline(s) you want to cover or uncheck the lifeline(s) you don't want to cover. Click OK button.
    Check Inspector Assistant
    Check Inspector Assistant

    As a result, the area of covered lifelines is extended or narrowed down according to your selection.
    The area of covered lifelines is extended
    The area of covered lifelines is extended

Managing Operands

After you've created a combined fragment on the messages, you can also add or remove operand(s).

  1. Move the mouse over the combined fragment and select Operand > Manage Operands... from the pop-up menu.
    Manage operands
    Manage operands
  2. To remove an operand, select the target operand from Operands and click Remove button. Click OK button.
    Remove Operand
    Remove Operand

    Otherwise, click Add button to add a new operand and then name it. Click OK button.

 

Developing sequence diagram with quick editor or keyboard shortcuts

In sequence diagram, an editor appears at the bottom of diagram by default, which enables you to construct sequence diagram with the buttons there. The shortcut keys assigned to the buttons provide a way to construct diagram through keyboard. Besides constructing diagram, you can also access diagram elements listing in the editor.

The quick editor
The quick editor

Editing lifelines

There are two panes, Lifelines and Messages. The Lifelines pane enables you to create different kinds of actors and lifelines.

Lifelines pane in quick editor
Lifelines pane in quick editor
Button
Shortcut
Description
Alt-Shift-A To create an actor
Alt-Shift-L To create a general lifeline
Alt-Shift-E To create an <<entity>> lifeline
Alt-Shift-C To create a <<control>> lifeline
Alt-Shift-B To create a <<boundary>> lifeline
Alt-Shift-O To open the specification of the element chosen in quick editor
Ctrl-Del To delete the element chosen in quick editor
Ctrl-L To link with the diagram, which cause the diagram element to be selected when selecting an element in editor, and vice versa

Buttons in Lifelines pane

Editing messages

The Messages pane enables you to connect lifelines with various kinds of messages.

Messages pane in quick editor
Messages pane in quick editor
Button Shortcut Description

Alt-Shift-M To create a message that connects actors/lifelines in diagram
Alt-Shift-D To create a duration message that connects actors/lifelines in diagram

Alt-Shift-C To create a create message that connects actors/lifelines in diagram
Alt-Shift-S To create a self message on an actor/lifeline in diagram
Alt-Shift-R To create a recursive message on an actor/lifeline in diagram
Alt-Shift-F To create a found message that connects to an actor/lifeline
Alt-Shift-L To create a lost message from an actor/lifeline
Alt-Shift-E To create a reentrant message that connects actors/lifelines in diagram
Ctrl-Shift-Up To swap the chosen message with the one above
Ctrl-Shift-Down To swap the chosen message with the one below
Ctrl-R To revert the direction of chosen message
Alt-Shift-O To open the specification of the message chosen in quick editor
Ctrl-Del To delete the message chosen in quick editor
Ctrl-L To link with the diagram, which cause the message to be selected when selecting a message in editor, and vice versa
Buttons in Messages pane

Expanding and collapsing the editor

To hide the editor, click on the down arrow button that appears at the bar on top of the quick editor. To expand, click on the up arrow button.

Collapse the quick editor
Collapse the quick editor

Setting different ways of numbering sequence messages

You are able to set the way of numbering sequence messages either on diagram base or frame base.

Diagram-based sequence message

Right click on the diagram's background, select Sequence Number and then either Single Level or Nested Level from the pop-up menu.

Diagram-based pop-up menu
Diagram-based pop-up menu

If you choose Single Level, all sequence messages will be ordered with integers on diagram base. On the other hand, if you choose Nested Level, all sequence messages will be ordered with decimal place on diagram base.

Single level
Single level

Frame-based sequence message

Right click on the diagram's background, select Sequence Number and then either Frame-based Single Level or Frame-based Nested Level from the pop-up menu.

Frame-based pop-up menu
Frame-based pop-up menu

When you set the way of numbering sequence messages on frame base, the sequence messages in frame will restart numbering sequence message since they are independent and ignore the way of numbering sequence message outside the frame.

Frame-based nested level
Frame-based nested level

Related Resources

The following resources may help you to learn more about the topic discussed in this page.

 
Chapter 3. Sequence diagram Table of Contents Chapter 4. Communication diagram
 

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