Hi all, i have a question concerning facts hierarchy, i'm looking for some hint as i suppose the same problem could have been faced by someone on the list.

I try to eplain with an example:

- Suppose to have a tree of facts, each object representing an UI widget.

   <root>

    <A id="1">

          <B />

    </A>

    <A id="2">

          <B />

    </A>

  </root>

- The individual elements A(1), B, A(2), B are mapped to facts, that are inserted in a KnowledgeStatefulSession

- A rule exists that states that when an object A is selected, the B object is automatically selected

- An event occurs that causes selection of node A(1)

The expected result is, obviously, that only the B element that is descendant of A(1) must be automatically selected

I'm trying a way to express the 'descendant' relationship in LHS construct.

The rule will look like:

rule "A requires B"

when

$fact1: NodeFact(id == "A", selected == true)

$fact2: NodeFact(id == "B", selected == false,  this DESCENDANT-OF $fact1)

then

$fact2.setSelected(true);

end

What is, in your opinion, the best way to handle this situation? What should replace the fake "DESCENDANT-OF" match?

Do i need to use a function that returns the list of descendant nodes of $fact1 and then match $fact2 against that? 

Will this be fast when dealing with large trees?

Any suggestion will be appreciated, thank you.

Giovanni

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