You can create UML Sequence diagrams.
UML Sequence Diagram Sample

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Diagram Properties

You can set the diagram property such as visibility settings from the property view (left-bottom pane).
UML-Sequence-Diagram-Sample-Property-view

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Automatic Diagram Layout

Since version 8.5 of Astah Professional and Astah UML, automatic diagram layout is available.
To use the auto-layout, go to [Alignment] – [Auto Layout] – [Vertical / Horizontal].
Automatic Layout for UML Sequence diagrams

However, this auto-layout does not work for CombinedFragments. Therefore, you will have to relocate CombinedFragments by hand after all. So using [Gap Expander] and [Gap Remover] options may work better if your Sequence diagram contains several CombinedFragments.
Sequence Diagram - Gap Expander

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Lifeline

You can create a lifeline by double-clicking on a diagram or choosing one from the tool palette and click on diagram.
UML Sequence Diagram Lifeline

Since version 9.2, you can create a Lifeline by dragging a Component from the tree view and drop it on the diagram.
Create a Lifeline by drag and drop of Component

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Adding a BaseClass

There are three ways to add a base class to Lifeline.

1. Directly type in a Lifeline

You can add a base class to Lifeline box by directly typing its Class (Block) name after the Lifeline name.
Add a baseclass to lifeline

2. From Lifeline’s property view

  1. Select a Lifeline.
  2. Go to the property view (Left-bottom pane) and click [New] button.
    add-baseclass-to-lifeline

  3. A pop-up appears where you can specify a class.

3. Drag a Class to Lifeline

You can drag a Class to Sequence diagram to create a lifeline with the class as its base class.
Dragging a Class to create a Lifeline on Sequence Diagram

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Show Actor as Lifeline

By dragging an Actor from the tree to diagram, you can represent lifeline in Actor on the Sequence Diagram.
Actor as Lifeline

Actor as a Lifeline

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Adjust Lifeline length

After creating a Sequence diagram, you may want to adjust the length of Lifelines to clean up the diagram. Right-click on a diagram then select [Adjust Lifeline Length] and choose from these three options.
Changing Lifeline Length on Sequence Diagram

Options

Default
Make all the lifeline to the shortest possible.
Align to Minimum
Make all the lifeline to the same length as the shortest one on the diagram.
Align to Maximum
Make all the lifeline to the same length as the longest one on the diagram.
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ExecutionSpecification

Minimize Execution Specification’s length

To clean up Sequence diagrams, you can minimize the length of Execution Specifications.
Right-click on a diagram then select [Adjust ExecutionSpecification Length].
Adjusting Execution Specification lengths on Sequence Diagram

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Hide Execution Specification

You can hide the Execution Specifications.
Currently, this is available in Astah Professional, UML, and System Safety editions only.

Hiding Execution Specification on Lifelines

1. Click anywhere on a diagram.
2. A property view for the Sequence diagram opens in the left-bottom pane.
3. Tick off the [Execution Specification Visibility].
Hiding execution specification on Lifelines

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Message

Found Message

You can create a Found message.

  1. Select [Synchronous Message] or [Asynchronous Message] from the tool palette.
  2. Click on a diagram
  3. Click on a target lifeline.
    Found Message

Lost Message

You can create a Lost Message.

  1. Select [Synchronous Message] or [Asynchronous Message] from the Tool palette.
  2. Click a Lifeline which you want it to be origin of this Message
  3. Click on a diagram.
    Lost message

Gate

You can create a Gate.

  1. Select [Synchronous Message] or [Asynchronous Message] from the Tool palette.
  2. Click on a diagram frame
  3. Click a Lifeline
    Gate

Reply Message

There are two ways to create Reply Messages.
Reply Message in Sequence Diagrams

Create manually

  1. Select [Reply Message] from a tool palette.
    Reply Message
  2. Click an ExecutionSpecification you want it to be an origin of Reply Message.

Create Automatically

  1. Turn on the [Reply Message Mode] on a tool palette.
    Reply Message Automatic Mode

  2. Create a Message
  3. Then a Reply Message will be generated automatically.
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CombinedFragment

You can create CombinedFragments.

  1. Select [CombinedFragement] from a tool palette.
  2. Specify the area where you want to create CombinedFragment. The area should include at least one Lifeline.

    CombinedFragment

Add an Operand

There are two ways to add Operands to CombinedFragments.

Create from pop-up menu
  1. Right-click on a CombinedFragment.
  2. Select [Add operand].
    Add operands
Create from Property View
  1. Select a CombinedFragment on diagram.
  2. Go to the property view (bottom pane) and choose [Operand] tab.
  3. Click [Add] button to add operands.
    Add Operands to CombinedFragments

    CombinedFragments_with_operands

TIPS: Define loop in the CombinedFragment

You can enter texts and numbers from the CombinedFragment’s Property View.
loop
loop

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InteractionUse

You can create InteractionUse.

  1. Select [InteractionUse] on a tool palette.
  2. Drag to specify where you want to place the InteractionUse.
    InteractionUse