Clarify a Limitation for Inferred Entity Instances

Question

Hi,
Under the section "Write rules that infer relationships and entities" in the User Guide there is the
Notes /Limitations
1) Combining manually created instances with inferred instances is not allowed.
2) Combining inferred entity instances with temporal values is not supported.
3) Only a single attribute of the entity instance can be inferred as a part of the entity rule. For example, the type of benefit ("unemployment benefit") can be set but the amount of the benefit would have to be set via a separate rule.
4) Inferred entity instances may not contain base level attributes.
5) A relationship that participates in an inferred entity instance rule is considered to be an inferred relationship. This means that an inferred relationship rule cannot be used to prove the same relationship used in an inferred entity instance rule.
Can number 4 be explained in a little more detail?
Thanks

Answer 1

I'm not sure I understand the question so I'm going to guess what you're asking by suggesting a business scenario and talk about how that would work. It is always much easier to talk about a specific business requirement you have rather than product features in general - so if you have a specific requirement I strongly recommend sharing it as you'll get better quality help.
Anyway, if we keep our existing example of an inferred entity "the product" (has attributes: the name of the product, the price of the product). Say we want to know want the price of the most expensive product you have selected (a concept which would be represented by an attribute at the global level).
You can do that. The rules to do that are just the same as the rules you'd use if instead of inferring the products and prices you instead asked the user to provide them (ie instancemaximum across a relationship). I'd send an example showing these rules - but it's not possible to attach files to this forum. You use inferred entities in the rest of your rules as if they had been input by a user - there's no difference. The key difference between an inferred entity and a non-inferred entity is that you can't collect more information about it (ie it can't have any base level attributes).
You can use any attribute in a rule so long as the usage of the attribute matches the entity level of the conclusion. ie You couldn't use "the price of the product" directly in a rule with a conclusion at the global level - because you revert to the problem of "the price of which product?".
On the off chance that this is somehow a "programmer" question (ie you're trying to understand how OPA works by treating it the same as another method for creating programs, for example a programming language like Java) - attributes in OPA don't have a concept of "private" and "public". If I tried to put OPA In those terms (and it's a stretch because OPA is not Java) - in OPA: everything is public (declare once use everywhere). An entity model in OPA is different thing to a class hierarchy.