How to determine if an object is an instance of a certain class in IBM Rules Designer/ODM?

Question

This may be an easy one, but I haven't found an easy way to determine in a rule that an object in working memory represented by an implemented interface is a specific class in IBM Rules Designer 8.8.1. For example, assuming HousingPeriod is an interface, if I have a definition that states:

definitions
    set 'the housing period' to a housing period...

And I want to follow that with a where clause that further refines the collection of objects that implement HousingPeriod as one of a list of implementing classes, say CollegeHousingPeriod and InternshipHousingPeriod, how could I do that? Something like:

        where this housing period is a college housing period

or

        where any of the following is true:
            - this housing period is a college housing period
            - this housing period is an internship housing period,

doesn't seem to work. Thanks in advance for any help you can provide!

Answer 1

As far as I know there is no built in way to query the type of an object. Instead I see two possible ways to get the desired result:

Create a virtual BOM entry with a custom B2X-mapping for each of your implementing classes. In the B2X-Mapping, you implement the necessary Java code to compare the object type and return a boolean. Verbalization would be something like {1} is a college housing period. This obviously only works if you know the objects before and there are not too many of them.

Option two is to not create different objects but to use a seperate attribute to distinguish housing period types. The verbalization would then be something like where the type of this housing period is college housing. With this approach you’d have to change the interface of your rules project, which might not be possible for you.