Quick'n dirty I could make drools 3 do it the way I would prefer - in
the context of my current problem and datastructures involved - by
modifying:
org.drools.reteoo.WorkingMemoryImpl, line 95f (rev. 3509):
replace:
/** Object-to-handle mapping. */
private Map identityMap
= new IdentityMap();
by:
/** Object-to-handle mapping. */
private Map identityMap
= new java.util.HashMap();
(not considering side effects, identityMap type cast problems, ...)
Then org.drools.reteoo.WorkingMemoryImpl, assertObject (line 422, rev.
3509):
FactHandleImpl handle = (FactHandleImpl) this.identityMap.get( object );
would return first "A"s handle when the second "A" is asserted, refering
to the example in my former posting.
I expected some way to customize the behaviour of the working memory,
basically by choosing between either of the Maps.
But as mentioned, such behaviour might not be desirable by others (they
probably want "A" being asserted twice and handled as two different
objects) and even if not customizable in drools itself, it can most
likely be done by wrapping assertObject and managing your own
object-to-handle map plus taking care not to use assert directly in RHS.
I first wrongly thought logical assertions had something to do with
this, but I guess that relates more to the 'logical' conditional element
in jess and logical dependencies among facts.
Michael Neale wrote:
what is your expectations on how it should work? (everyone has different
ideas it seems !)
On 4/10/06, Juergen <[EMAIL PROTECTED]> wrote:
I mean
workingMemory.assertObject(new String("A"));
workingMemory.assertObject(new String("A"));
would currently assert both strings into working memory, whereas if it
would check not for identityHashCode but with equals, the second assert
would have no effect.
When during experimentation with rule engines I switched from jess
(where it is done with equals I think) to drools 2 I first experienced
problems due to this differences (also did not find much in both engines
docu), leading to my question if I could customize drools behaviour.
As one can always write a wrapper for drools assertObject to make such
checks, and lots of other users probably dont need, my request is not
important.
Juergen
Michael Neale wrote:
so you mean
p1 : Person()
p2 : Person()
eval ( p1.equals(p2) )
(but presumably a shorthand form?)
On 4/8/06, Mark Proctor <[EMAIL PROTECTED]> wrote:
We hadn't planned it, not promising anything - but I'll see how things
pan out, may be we will get time.
Mark
Juergen wrote:
ad. Can object equality for assertion be customized?
Drools 3 still seems to use IdentityMap with System.identityHashCode().
Is it planned to be customizeable e.g. with equals() in 3.0?
Michael Neale wrote:
Short answer, not easily with Drools 2. But yes, with Drools 3.
On 3/22/06, Juergen <[EMAIL PROTECTED]> wrote:
I recently looked into drools after experimenting with JESS and got a
few questions I could not look up in the drools documentation:
- Exists a condition to test for non-existence of a matching
object/fact?
-- If yes, how to use it for own domain specific language conditions
- How is sharing of conditions/nodes between productions implemented
in
drools, one of the main benefits of the rete algorithm?
-- How is the equality of conditions defined for java smf? via
textual
equality of the condition's java code?
-- How can equality of conditions for sharing be defined for domain
specific language conditions?
e.g. Conway's game of life (slightly modified dsl)
<rule name="kill the overcrowded">
<conway:cellIsAlive cellName="cell"/>
<conway:cellIsOverCrowded cellName="cell"/>
<conway:killCell cellName="cell"/>
</rule>
<rule name="kill the lonely">
<conway:cellIsAlive cellName="cell"/>
<conway:cellIsLonely cellName="cell"/>
<conway:killCell cellName="cell"/>
</rule>
The conway:cellIsAlive condition could be shared between these two
productions. Would it?
- When will the properties map be supported in drools implementation
of
JSR 94 javax.rules API?
-- e.g. to be able to set conflict resolver of a rule base and other
settings that can be set via drools native API
- Can object equality for assertion be customized?
-- Currently, org.drools.util.IdentityMap
(org.drools.reteoo.WorkingMemoryImpl) makes use of
System.identityHashCode(). There seems to be no way to customize
that,
e.g. make drools use equals() instead, neither via native nor JSR 94
API.
My apologies if some questions have already been answered in other
postings, I made no thorough search in this newsgroup yet.
Thanks a lot, Juergen
