Queries and backward-chaining
Queries were introduced in Chapter 5, Understanding KIE Sessions, as a way to retrieve information from a KIE Session. But queries are much more powerful than that in Drools. As a matter of fact, queries are the way Drools implements what is called backward-chaining reasoning. But before entering this new topic, and given that we were already talking about PHREAK, let's see how a regular query looks in the PHREAK network.
For this section of the book, we are going to introduce a new Java class that will be used to establish a whole-part relationship between
Item objects. What this means it that an
Item can now be composed of other
The whole-part relationship between
Items is modeled as a generic class, called ...