Declarative Interview Questions Part 3

  1. What do you mean by Declare constraints ?

Ans : Constraints rules are used to define and enforce comparison relationships among property values. Constraints rules can provide an automatic form of property validation every time the property’s value is “touched”,


  1. What is forward chaining in PEGA ?

Ans : Forward chaining allows for the automatic propagation of changes in one property value to changes in other property values or to indexes

For example “:The way the system evaluates constraints automatically each time a property identified in a constraints rule is changed is known as Forward chaining.


  1. Give some example where forward chaining are used ?

Ans : Declare Expression rules with Whenever inputs change ; Declare Trigger and Declare OnChange rules.


  1. What is backward chaining ?

Ans : Backward chaining executes Declare Expression rules when a value is needed for a property, rather than when inputs change.


  1. Give an example where backward chaining works ?

ANS : Backward chaining applies to Declare Expression rules

When used if no value present

When used, if property is missing

Whenever used

  1. Do you have any idea about Locatable page ? Where these are used ?

Ans :  locatable pages reduces the need for pages to be explicitly named in the rule. Locatable pages can be used with Constraints rules and Declare Expression rules. There is no need to use when condition if you use this feature in backward chaining.


  1. How rule resolution works when it looks for Declartives ?

Ans : First Filters candidate rules based on a requestor’s RuleSet list of RuleSets and Versions

Then Searches through ancestor classes in the class hierarchy for candidates when no matching rule is found in the starting class


8.Can you circumstance a declarative rule ?

Ans : Yes we can do.


  1. What can cause declarative rules to be re evaluated ?

Ans :When a circumstance property’s value changes, the declarative network re-evaluates the expression or constraint. However, if a circumstance property reference uses a top-level page name, changing that property’s value does not cause the declarative network to re-evaluate the expression or constraint.


  1. What do you mean by Context-free expression rules

Ans : A context-free expression rule is a Declare Expression rule that applies to an embedded page or pages. It computes the value of a target property in every page of that class that appears on the clipboard, regardless of the name, class or content of higher-level pages above the embedded page

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