Working with Sequence Flows

The sequence flow determines the execution sequence of activities. A sequence flow connects an element with its successor element. It also allows setting a condition - only if this condition is fulfilled at runtime the transition is processed and the next activity is executed.

This chapter covers the following:

• Rules for Connecting Elements
• Sequence Flow Activation and Deactivation
  • Viewing Sequence Flow Properties
• Conditional Sequence Flow
  • Viewing Properties of Conditional Sequence Flow

Rules for Connecting Elements

Following are the rules which need to be followed when connecting two elements:

• A maximum of one in and one out connection can be established between the same two elements.
• A connection must connect two different elements.
• Connections can be rerouted after they are established.

Event Connections

• Only out sequence flow connections are allowed on Start Events
• Only in sequence flow connections are allowed on End Events
• Each Event can have only one sequence flow connection. Multiple connections are not allowed from events.
• Events can be connected only to activities and gateways
• Data connections/associations are not supported.

Activity Connections

• Each activity can have a maximum of one in and one out sequence flow connector, except for Start Events.
• An unlimited number of in and out data connections/associations can be established, but only one in and one out per data symbol should be allowed.

Gateway Connections

• Unlimited in and out sequence flow connections can be established
• Data connections/associations are not supported
• Incoming connections are sequence flow connections and display the Sequence Flow Property Panel when clicked.
• Outgoing connections allow specification of Conditional Expression/Default Sequence Flow in the property panel.

Sequence Flow Activation and Deactivation

The connect mode of the sequence flow is activated by:

• Creating Sequence Flow from Main Toolbar
• Creating Sequence Flow from Flyout Menu of all the Elements

Creating Sequence Flow from Main Toolbar

Click the Create Connector icon in the main toolbar and hover the mouse over element. The starting and ending anchor points are established. Click on the elements between which you want to establish the sequence flow.

Figure: End Point - Connector

Creating Sequence Flow from Flyout Menu of all the Elements

When you hover the mouse over following elements the flyout menu gets activated.

• Activities of all types
• Gateways
• Data
• Start Event

You can connect elements using the flyout menu of each element.

Viewing Sequence Flow Properties

To view the sequence flow properties, click on the sequence flow.

Figure: Sequence Flow

The General Properties of a sequence flow gets displayed. You can specify description for the sequence flow.

Figure: Sequence Flow

Click the Transactional Behavior icon displayed at the left side of the General Properties pane of the Sequence Flow. The Transactional Behavior properties of the sequence flow get displayed.

Figure: Sequence Flow - Transactional Behavior

Select the Fork Transaction on Traversal check box to see the traversing during transition conditions. This option of a transition controls the synchronization and concurrency behavior during the execution of the corresponding process instances. Please refer to the section Activity Thread Activity Thread of the chapter Runtime Behavior Runtime Behavior in the Stardust Documentation for detailed information on the Fork Transaction on Traversal functionality.

Click the Comments icon displayed at the top left side of the General Properties pane of the Sequence Flow. Specify the comment in the text box and click Submit. The newest comment gets displayed at the top of the table. To delete the comment, select the comment and click the Delete icon. The user, who has submitted the comment, only that user can delete the comment. If the other user selects the comment or no comment is selected, the Delete icon remains in disabled state.

Figure: Sequence Flow - Comment

Conditional Sequence Flow

The conditional sequence flow gets created on outgoing connection from gateway. The Web-based modeler supports setting conditional sequence flow only from gateways to activities. In place editing is not available for sequence flow.

Figure: Conditional Sequence Flow

You can specify conditional expressions only on outgoing connections of gateways.

Viewing Properties of Conditional Sequence Flow

Click on the conditional sequence flow to view its properties.

Figure: Conditional Sequence Flow - General Properties

• UUID - A unique identifier ID gets generated as an identifier for client server communication
• ID - An ID generated automatically based on the conditional sequence flow name. If element with the same name exists then during ID generation, a numerical suffix gets added to the ID. If the element is renamed, the ID gets regenerated.

The UUID and ID options are displayed only when you switch to Integrator profile.

• Name - Though you specify the name for conditional sequence flow, it will not be displayed in the process diagram canvas. Only condition expression gets displayed.
• Description - Specify description in the text box.
• Default Flow - The sequence flow is the "default" (i.e., OTHERWISE) when the Default Flow check box is marked. By default, this check box is not selected. If you select this check box, the sequence flow is always evaluated to true though all the other conditions on the split have the value false. The Condition Expression editor displays the value true. The sequence flow with slash through indicates that it is a default sequence flow.


Figure: Default Sequence Flow

• Condition Expression - You can specify a condition in this editor. The sequence is then traversed and the next activity is performed, if the specified condition is fulfilled. Conditions are specified if the successor activity is only to be performed under particular circumstances. If the return value of a transition condition is true, the sequence will always be traversed and the successor activity executed. A JavaScript based editor is provided to add arithmetic, relational and logical operators as well as string matching operators. Note that conditional expression is not supported for activity to activity sequence flow in Web-based modeler.