Sequence Diagram

Overview

Sequence diagrams can be used to visualize the flow of mutual processing between objects.
This page explains the operations for using sequence diagrams in the following order.

• Place sequence diagram
• Define your lifeline
• Define the message
• Define a compound fragment
• Define interaction usage

We also provide the following features to assist users in their modeling:
These will also be explained in turn.

• Validate the model
• Set display content

Place the sequence diagram

To place a sequence diagram, follow these steps:

Operating instructions

1. Select the package in the model navigator and click [Add Model] > [Sequence Diagram] in the context menu.
2. The sequence diagram is placed as a child element of the selected package.

Define lifeline

To define a lifeline, follow these steps:

Operating instructions

1. Select an existing class in the model navigator and drag and drop it onto the sequence diagram.
2. A new lifeline with the selected class as its type is created in the displayed sequence diagram.

Elements that can be added from the toolbox

You can add the following elements displayed in the toolbox to the sequence diagram.

Icon	Name
	Lifeline
	Composite fragment
	Use of Interaction
	Interaction Note
	Destruction

Define an untyped lifeline

You can create a lifeline without a type by dragging and dropping [Lifeline] from the toolbox onto the sequence diagram.

tip

To change the lifeline type, select the lifeline on the sequence diagram and click [Change lifeline type] on the context menu.

Lifeline types that can be set
A lifeline type can have the following elements:

Icon	Name
	Class
	Interface
	Component
	Actor
	Block

Define the message

To define a message, follow these steps:

Operating instructions

1. In the sequence diagram, when you hover your mouse over a lifeline, a black triangle icon will appear.
2. Drag and drop the displayed icon towards the target lifeline.
3. When the finder appears, select the operation corresponding to the message and press the [OK] button.
4. A synchronization message is created for the target lifeline.

Elements that can be added from the toolbox

You can add the following elements displayed in the sub toolbox to the sequence diagram.

Icon	Name
	Synchronized message
	Asynchronous Message
	Reply Message
	CreateMessage
	Discard message

When adding these messages, select the type of message you want to add in the sub toolbox and then add the message.

About message text notation

If you enter a message operation as text on a sequence diagram, the text will be analyzed according to the notation format of the message operation.
Of course, if you change each field value, it will be reflected in the text on the diagram.

Correspondence between message text representation format and each field value
Messages are displayed and parsed as text according to the following format:

• For request messages (other than response messages)
  <Request message> ::= <Message name> ['('[<List of arguments>] ')'] [':'<Return value type>]
  • supplement
    • <List of arguments> is displayed in the following format.
      • <List of arguments> ::= <Arguments> [','<Arguments>]*
      • <Argument> ::= [<Argument name> '='] <Argument value> | '-'
  • Example
    Message name: Drive
    Argument 1 name: m, value: 100
    Argument 2 name: s, value: 200
    Return type: boolean
    In this case, the following text will be displayed.
    Drive(m=100, s=200) : boolean
  • Note
    • <return type> is ignored when setting.
• For response messages
  <Response message> ::= [<Return value variable name> '='] <Message name>['(' [<List of arguments>] ')'] [':' <Return value>]
  • supplement
    • <List of arguments> is displayed in the following format.
      • <List of arguments> ::= <Arguments> [','<Arguments>]*
      • <Argument> ::= [<Argument variable name> '='] <Argument name> [':' <Argument value>]
  • Example
    Return value variable name: return_value, return value: true
    Message name: Drive
    Argument 1 variable name: miles, argument name: m, value: 200
    Argument 2 variable name: speed, argument name: s, value: 100
    In this case, the following text will be displayed.
    return_value=Drive(miles=m:200, speed:s=100) : true

tip

To change the action for a message, select the message and click Change Message Type on the context menu.

Define composite fragment

To define a composite fragment, follow these steps:

Operating instructions

1. Select the composite fragment in the toolbox and drag and drop it onto the sequence diagram.
2. Double-click the top left of the added composite fragment to display a drop-down list of types and select the type of composite fragment to add.

List of compound fragment types

Composite fragments can be of the following types:

Change Shape Type	Meaning
alt	Alternative
opt	Option
loop	Loop
par	Parallel
break	Break
neg	negation
strict	strict
seq	seq
ignore	ignore
consider	consider
assert	Assert

Define interaction usage

To define interaction usage, follow these steps:

Operating instructions

1. Select Use Interaction in the toolbox and drag and drop it onto the sequence diagram.
2. Select the use of the added interaction and associate the sequence diagram to be referenced with [Associate Interaction] from the context menu.

tip

To jump to the sequence diagram associated with an interaction usage, select the interaction usage and click Show Associated Interactions in the context menu.

Validate the model

The contents verified by the sequence diagram are as follows.

• Is the operation associated with the message available for the destination lifeline type?

info

For example, you can detect inconsistencies between the operation associated with a message and the type of the destination lifeline as a result of the following changes:

1. Specify the operation defined in the inheritance source class of the class that is the type of the destination lifeline as the operation associated with the message.
2. Delete the inheritance relationship of the class that is the type of the destination lifeline using a class diagram, etc.

To validate your model, follow these steps:

Operating instructions

1. Run UML > Validation > Check Consistency from the ribbon.
2. If an inconsistency is detected in the messages placed in the sequence diagram, an error will be displayed.

tip

Click the [Home] > [Model] > [Check Error] button on the ribbon to perform validation on all models in addition to the standard validation.

Set display content

You can display only the information of interest in sequence diagrams without changing the model.
To set the display contents of the arguments corresponding to the request message, follow the steps below.

Operating instructions

1. Display the sequence diagram whose display you want to switch.
2. Select the argument checkbox in the Request Message group on the UML Diagram tab in the Inspector.

Elements whose display can be switched

You can switch the display of the following elements in sequence diagrams.

Category	Element
Request message	Arguments
	Argument name
	Return type
Response message	Argument
	Argument value
	Argument assignment variables
	Return value
	Return value variable

Restrictions

• State invariant expressions and duration constraints cannot be defined.
• It is not possible to connect messages from frames.
• Cannot connect messages to interaction usage.
• Copying and pasting of elements is not possible.
• The order of messages in a sequence (commonly called GeneralOrdering) is represented only by the Y coordinate on the diagram. If you use the difference comparison function, you cannot check the differences as a model.
• Stereotypes are not represented on sequence diagrams.