Sequence Diagram Online

Posted : admin On 1/18/2022

An alternative combined fragment is used to specify an area of a group of lifelines/ actors to show conditional flow in a sequence diagram. It also models the if-then-else logic in the sequence diagram. In this article, we will demonstrate how to draw a simple sequence diagram by using an alternative combined fragment.

  1. Create a sequence diagram as follows:
  2. Select Alt. Combined Fragment in the diagram toolbar. Press on the blank area of the diagram and drag to cover the Person and ATM Machine lifeline.

    Create an alternative combined fragment

  3. Draw a message from ATM Machine lifeline to Person lifeline in the upper compartment of the alternative combined fragment. Name it as Ask for password. Draw another message from ATM Machine lifeline to Person lifeline in the lower compartment of the alternative combined fragment afterwards. Name it as Display invalid card.

    Draw two messages in an alternative combined fragment

  4. Right-click on the combined fragment and select Open Specification… from the pop-up menu to open the Combined Fragment Specification dialog box.
  5. When the Combined Fragments Specification window appears, open the Interaction Operands tab, select Operand, and then click Open Specification… button. In the Interaction Operand Specification dialog box, open the Guard tab and enter Valid card in Constraint text field. Click OK button to confirm the changes.

    Enter Valid card for Operand

  6. Similarly, enter Invalid card in Constraint text field for Operand2by following the previous step.
  7. Guard conditions are displayed in the alternative combined fragment as shown below:

    Guard conditions are displayed

Sequence Diagram Online Tools is a completely free online tool for creating sequence diagrams. The graphic design is created by All processing of parsing and painting the diagram is done using javascript client side in the user's web browser. This not only makes it snappy to work with, but it also means that your secrets are safe. Draw sequence diagrams in seconds using this free online tool.


Sequence Diagram Online Draw

How to try the sample

Sequence Diagram online, free

Download ATM machine and then unzip it to get the .vpp file.