[rules-users] Insert new facts in WorkingMemory event handler

[Gabor Szokoli]

I think I've got your use case: you are making XSLT on steroi^W some
kind of cheese that tastes stimulating and is dense in nutrients but
is in no way controversial.
It would allow user rules for removing stuff, and have built-in rules
for transitively removing unreferenced stuff, right?

On Mon, Dec 6, 2010 at 12:19 PM, Bruno Freudensprung
<bruno.freudensprung at temis.com> wrote:
> I simply plan to read my XML and add the corresponding objects into
> the session, then to fire the rules.

Ahh, silly me, rule processing is externally initiated in Drools, it's
not some kind of perpetual event engine.

> Well... I wanted to delegate the whole "logic" to Drools and I imagined
> that I could "listen" to Drools' WorkingMemory's retraction events in
> order to remove the corresponding elements from the input XML.

Would a query work instead of the event listener then?
I guess it would if the list of remaining stuff is good too...
Or you could mark the unneeded stuff instead of retracting, reason
over the marks, and be able to query the marked stuff directly:

rule "orphaned Type"
when
       t : T(mark != true)
       not I(type == t, mark == true)
then
       modify (t) {setMark(true)}
end

rule "orphaned Instance"
when
       t : T(mark == true)
       I(type == t, mark != true)

then
       modify(i) {setMark(true)}
end

// transform your rules "1" and "2" as well to sanitize input!

query "types to delete"
       t : T(mark == true)
end

query "instances to delete"
       i : I(mark == true)
end