Rule Event

Overview

Rule events can be added to a process model in one of two ways. They can either be added to the process flow as a process node, or they can be used within an activity to trigger an exception flow.

At any time in a process model when there are certain conditions that need to be met before the process flow proceeds, an intermediate rule event should be used. Once an intermediate rule event is activated, it remains active until the rule evaluates to true.

Properties

• Category: Events

• Icon:

• Compatible with autoscale: Yes *

Configuring a Rule Event

To configure a Rule Event:

1. In the Process Modeler, select and drag the Rule Event node from the palette to the canvas.
2. Connect it to your process model.
3. Double-click the Rule Event node. The Rule Event dialog box displays.
4. Type a name for your event.
5. Select the Setup tab.
6. Select New Condition or New Expression.

With an expression, you can use a Rule Event to monitor global constants and process variables. Each time a global constant or process variable is changed, the rule is reevaluated.

Best Practice: As a best practice, we recommend using conditions rather than expressions whenever possible because conditions consume fewer processing resources and less memory than expressions.

Building a Rule Event condition

To build a Rule Event condition:

1. Click New Condition on the toolbar. A row is added to the Rules to Continue Flow list.
2. Click the first list box.
   • A list of process variables is displayed.
3. Select the process variable you want to use as a comparison value.

4. In the second list box, select the operator you wish to use for the condition. The following options are available:

   Select	To perform this operation…
   =	equals to
   <>	not equal to
   <	less than
   >	greater than
   <=	less than or equal to
   >=	greater than or equal to

5. In the text-entry field, type the value you want to compare against the process variable selected in step two.

Creating an expression

To create an expression:

1. Click New Expression from the toolbar. A row is added to the Rules to Continue Flow list, containing a text-entry field and the Expression Editor button.
2. Click to display the Expression Editor.
3. Select the Rules & Constants tab.
4. Select a rule to use from the displayed list - OR - Create a new expression using the process variables and properties listed on the Data tab and the logical functions listed on the Functions tab.

   Note:  Expressions that are created as a rule must evaluate to true or false. Creating an expression that does not evaluate to true or false causes the expression to be automatically set to false.

5. Save the expression for reuse by clicking Save as new expression rule.

Usage considerations

Autoscale

In autoscaled processes, rule events are evaluated only when the node is first activated. If the rule evaluates to true at that point, the exception flow is taken and the node status is set to Skipped.

Run at low throughput in autoscaled processes

This smart service is not intended for high-throughput usage and should only be used at low frequency in processes with autoscale enabled. The underlying services this node relies on may not scale to the same degree as autoscale-enabled processes, which may impact performance at high concurrency.

For autoscaled processes, consider one or more of these approaches:

• Position this node in less used paths within your process flow. This could be an exception path or an uncommon case for the process.
• Monitor node execution times during performance testing to see if the node performs differently at scale.

When used in an autoscaled process, the node should behave as it would in a standard process of comparable scale. For typical workloads, no special design considerations are needed.

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