Re: [rules-users] Drools + EMF + CDO
Several remarks:
(1) Make sure that a parent is asserted after all of its children. Otherwise
initial evaluation will not comprise the entire children's list.
(2) After changing a child's state, update the parent.
(3) The rule as you have it now is somewhat circumstantial. A simpler
approach would be
rule NoUpChild
when
$p : Device( $children : eContents, eContents.size > 0 )
not( Device( state == "UP" ) from $children )
then
System.out.println( $p.getId() + ": no child up" );
end
(4) If you have a "parent" field, this could even be written:
rule NoUpChild
when
$p : Device( children.size > 0 )
not( Device( parent == $p, state == "UP" ) )
then
System.out.println( $p.getId() + ": no child up" );
end
-W
2010/8/2 Georg Maier <Georg.Maier(a)cjt.de>
Hi,
I’m trying to figure out an issue for three days now and I’m getting kind
of desperate, so I hope someone can help.
I’m using Drools in combination with an EMF model which is modeling a
computer network. On init, I read the whole structure of the model and
insert all elements into the working memory. Some of the entities share the
super class “Device” which has an attribute “state”.
Now I’m having the following rule to change an attribute of one of the
model entities:
*rule* "Set received status to model"
*when*
$event : SomeEvent (
$hostname : hostname,
$hoststate : hoststate,
$timestamp : timestamp
)
$device : Device (
name == $hostname
)
*then*
*modify*($device) {
setState($hoststate);
}
db.commit(*false*);
*retract*($event);
System.err.println("Set status of " + $device + " to " +
$hoststate);
*end*
… which works perfectly fine. Anyway, what I want to do in this test case
is to *react whenever all child devices of a mutual parent device* (e.g.
hosts on one switch) are no longer reachable. I thought of a rule like the
following:
*rule* "Parent Children Test"
*when*
$parent : Device (
$children : eContents,
eContents.size > 0
)
*forall* (
$child : Device (
state == "DOWN"
) *from* $children
)
*then*
…
*end*
* *
… which by the way worked perfectly fine as long as I was not using objects
from a model. My first idea was that for some strange reason the object
might get copied so that I actually would have two different references
after modifying it, but this is not the case. When I initialize the rule
base with the circumstances that the second rule would fire, it really does.
It just seems as it would not being evaluated after changing the attribute,
but this is not the case either! So all I can think of is some strange
caching, maybe in combination with the *forall *statement? Maybe someone
has some experience when using Drools with EMF + CDO and experienced as
similar issue?
Any help would be very very very much appreciated!
Thanks in advance
Georg
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