Property-Seek-Value method

03-04 GENTJ Use this method to initiate backward chaining computations for the value of a property, based on Declare Expression rules.

For example, the standard activity Work-.VerifyProperty — referenced in the standard flow action Work-.VerifyProperty — calls this method.

Parameters

This method has four parameters:

Parameter	Description
GoalProperty	Identify the property to compute. This must be the Target Property key part of a Declare Expression rule.
AlwaysRecompute	Select to force the system to compute the value of the property identified in the GoalProperty parameter even when the property already is present on the clipboard and has a non-null value. In most cases, leave this box cleared, so that the Compute Value field in the Declare Expression rule applies.
AlwaysForwardChain	Select to cause the system to forward chain after backward chaining, even when the goal-seek attempt failed. If not selected, when goal seeking fails, any property changes made by the goal seek process are not considered for forward chaining. In most cases, leave this box cleared.
MissingReference Property	Optional. Enter a target property, a local variable, or an activity parameter. When backward chaining fails to compute the property identified in the GoalProperty parameter, the method stores name of the property that prevented the computation from completing there.

Results

This method uses backward chaining on the dependency network defined through Declare Expression rules to compute or recompute the value of the goal property.

The system uses the GoalProperty parameter and class of the step page (or primary page) as the Applies To key part to search for the Declare Expression rule. It then uses the Declare Expression rule to starts backward-chaining computations to obtain a value for the property. MIRAT 2/21/06

If backward chaining is successful, the result is a new value for the property identified in the GoalProperty parameter. (Other properties may also have new values, all consistent with Declare Expression rules and other declarative rules).

If the backward chaining computation is unable to compute a value for the GoalProperty property, it may return instead the name of another property (identified in the third parameter) that — if it had a value — could contribute to the computation. Your application may then prompt a user for a value for this property, or use other means to obtain this value.

For more information, see More about Declare Expression rules.

Checking the method status

This method updates the pxMethodStatus property. See How to test method results using a transition.

	backward chaining, dependency network
	About Declare Expression rules Declarative processing — Concepts and terms

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