See this topic in the Oracle Policy Modeling User's Guide, Write rules that infer relationships and entities.
"Rules that infer relationships and entities can be useful for grouping entity instances in order to refer to the group as a whole in your rules and use the standard entity functions in a more powerful way. For example, you could:
Collect payments and write rules to sum all payments made within the same year
Determine eligibility for benefits and write rules to sum all eligible benefits or create a payment plan for all eligible benefits
Collect product information and write rules to determine which services should be created based on the customer’s product
Further examples are provided under Worked Examples" in the topic Write rules that infer relationships and entities.
The basic example I like to use is determining eligibility for the children in the household. If you have the containment relationship "the children in the household", then the inferred relationship "the eligible children in the household" will be a subset of the children in the household, of whose membership is determined by one or more inferred attributes on each child. As the circumstances of a child changes, they will either be added or removed from the inferred relationship.
I like to use a even more basic example... List Of Clasifications
Lets assume that:
You are Rich if you make $200,000 or more:
You are American if you are born in the US
You completed a Bachelors degree if you studied more than 12yrs
You are not a felon if you never went to jail
and so on...
Now you have a "Entity" that is basically the list of classification (instead of having them as a attributes)
Now you can create a list of "type" based on the rule I described above...
Depending on the conditions met you would dynamically have the following:
Instance 1: Rich
Instance 2: American
Intance 3: Not a Felon
This is very good for integration with other systems