Declarative Processing

Declarative Processing

•Declarative processing simplifies your application and reduces the number of activities you must create
•Dynamic evaluation of properties based on the changes in dependent properties
•Checking the state of a property (constraint) automatically based on the changes in dependent properties
•Running a specified Activity automatically when the value of a property changes either during processing or upon database commit


Declarative Rules


•Declarative rules provide the necessary capabilities required necessary for declarative processing
•Dynamically retrieve the necessary data for the situation
•Reduce the need for complex procedural logic and manual exceptional handling
•Makes complex processes significantly easier to automate
•Deliver time and cost savings for both BPM and BRM solutions


•Constraints rules (Rule-Declare-Constraints rule type)
•Declare Expression rules (Rule-Declare-Expressions rule type)
•Declare Index rules (Rule-Declare-Index rule type)
•Declare OnChange rules (Rule-Declare-OnChange rule type)
•Declare Trigger rules (Rule-Declare-Trigger rule types)
•These rules belong to the Decision category.


•Declarative rules are not referenced explicitly in other rules. Use of a property that's referenced in an expression or constraint rule causes the expression or constraint rule (and perhaps many other rules) to run.
•Process Commander uses an inference engine and an internal data structure known as the dependency network to support declarative processing


FORWARD CHAINING


•Forward chaining provides the automatic propagation of changes in one property value to cause recomputations of another property's value
•E.g.:- Area = Length * Width
Volume = Area * Depth
The value of Volume is automatically recomputed whenever there is any change in Length, Width and Depth

For those Declare Expression rules that have Whenever inputs change in the Calculate Value field, the system creates an internal dependency network, identifying which properties have values that may depend on which other properties

Delegation

In addition, a Declare Expression rule can be delegated to business managers who have the PegaRULES:WorkMgr4 access role. The business managers can see and update only fields on the Expressions tab.

Backward Chaining


•Backwards chaining executes Declare Expression rules when a value is needed for a property, rather than when inputs change
•The Process of computing the values of one or more dependent properties in order to calculate the value of a property is known as GOAL SEEK. Currently available for Declare-Expression rules only.
•Backwards chaining applies to Declare Expression rules that have a Calculate Value field set to one of the following:

When used if no value present
When used, if property is missing
Whenever used

•E.g.:- Area= length* Width


If whenever used option is selected in the calculate value field then each time the system accesses the Area property for a value the Declare Expression rule recomputes
•Standard rules support experimentation with backwards chaining. The flow actions attempt to find a value for the pyResolutionCost property:

VerifyProperty flow action
VerifyPropertywithListing flow action
PromptGoalSeekProperty HTML rule
VerifyProperty activity