Heck, yeah, I'm up for it.  Rulesfest is over, so I'm bored. :P  

--- On Tue, 11/4/08, Edson Tirelli <tirelli@post.com> wrote:

From: Edson Tirelli <tirelli@post.com>
Subject: Re: [rules-users] Chart notation, update, and infinite loops
To: greg_barton@yahoo.com, "Rules Users List" <rules-users@lists.jboss.org>
Date: Tuesday, November 4, 2008, 7:54 PM
That is an excellent project, but it is deep in the core
engine. Great
opportunity to learn all about ReteOO and drools internals,
but will require
some research from your side... we know the general
solution, but you may
still find some obstacles that need to be removed as you
go.

   If you are willing to take the challenge, lets move the
discussion to
drools-dev and we can guide you.

   []s
   Edson

2008/11/4 Greg Barton <greg_barton@yahoo.com>

I thought drools had this.  If you point me in the

right direction (and you

have the time) I'd be happy to work on that.

--- On Tue, 11/4/08, Edson Tirelli

<tirelli@post.com> wrote:

From: Edson Tirelli <tirelli@post.com>
Subject: Re: [rules-users] Chart notation,

update, and infinite loops

To: "Rules Users List"

<rules-users@lists.jboss.org>

Date: Tuesday, November 4, 2008, 7:06 PM
Dan,

   This is a feature that is in our to-do list.

Jess calls

it "slot specific
updates". We did not had the time yet to

implement it

though. :(

   []s
   Edson

2008/11/4 Dan Seaver <dan.seaver@ge.com>

Your understanding is very close to what

I'm

looking for. I don't mind

having
multiple rule activations in other areas of

the

ruleset when the Fact is

updated, I just don't want the current

rule, the

one with the update

statement, to be reactivated.

Accumulate plus no-loop works fine for the

specific

case of updating

amounts, but I'd like to have something

generic

for more sophisticated

logic
that would be implemented in the

"then"

clause.

Maybe if there was something that looked

specifically

at each property of

the update? In this case, the

"when" clause

is looking at the "name"

property and the "then" clause is

updating

the "amount" property. As the

"name" is not being changed, then

the update

wouldn't reactivate the rule.

Greg Barton wrote:

If you have the control fact that

handles the

"applied == false"

condition

you wouldn't need to prevent

reactivation of

the rule.  It would be

handled by the condition.

I'm thinking Edson's accumulate

suggestion would be best, at this point.

If I understand correctly, what you

want is this:

1) One rule Fact/Charge activation per

Charge

instance, with no

reactivation when the Fact is updated.
2) Other Fact dependent rule

activations when the

Fact is updated.

The problem with making (1) happen is

that

you'd still have the matched

Fact being updated once per Charge,

which could

lead to reactivation of

the rules in (2) multiple times, which

you may

not want.  If you use

accumulate in the Fact/Charge rule,

plus no-loop

to prevent reactivation,

you get the best of both worlds: single

activation of the Fact/Charge

rule, with a single update to notify

other rules

that the Fact has

changed.

I think what you're after is some

kind of

"modify group," where multiple

calls to modify are counted as just

one, and

rules are notified when the

group is closed out.  I'm not sure

how that

would be implemented, because

how do you know when the modifications

are

finished?  A low priority

rule,

possibly?  Anyway, it doesn't exist

in

drools, afaik.

You could do that kind of thing with an

additional rule that tests for

the

nonexistence of an unprocessed Charge,

then does

the update.  Adding in

the control fact for tracking Charges:

rule "Update Amount"
   when
      amountFact : Fact(name ==

"Amount")

      $charge : Charge()
      chargeTracker :

ChargeTracker(charge ==

$charge, applied == false)

   then
      Double amount =

amountFact.getAmount();

      Double chargeAmount =

charge.getAmount();

      amountFact.setAmount(amount +

chargeAmount);

      chargeTracker.setApplied(true);
      update(charge);
end

rule "Close Facts After Charges

Applied"

   no-loop false
   when
      amountFact : Fact(name ==

"Amount")

      not ChargeTracker(applied ==

false)

   then
      update(amountFact);
end

You'd probablt also have to prevent

the

"Close Facts" rule from firing

when there's just no ChargeTrackers

in

working memory, too.

Give that a try.

--- On Tue, 11/4/08, Dan Seaver

<dan.seaver@ge.com> wrote:

From: Dan Seaver

<dan.seaver@ge.com>

Subject: Re: [rules-users] Chart

notation,

update, and infinite loops

To: rules-users@lists.jboss.org
Date: Tuesday, November 4, 2008,

1:55 PM

Greg,
1) Yes, in this case I'm

looking for the

cartesian

join.
2) No, I can't add a property

to Charge

as it's

part of our corp Object
Model.

However, I could create a third

object that

manages whether

the Charge has
been processed which works just

fine. Unless

there is a

simpler strategy /
technique, I'll go with that.

Do you know of any way to keep the

rule from

being put back

on the agenda
when amountFact is updated? I want

other

rules to know that

it's been
updated, just not the rule that

made the

change.

Dan

Greg Barton wrote:

1) Do you want to apply all

Charges in

working memory

to all "Amount"

Facts?  I ask because the rule

is a

cartesian join

(i.e. no relation

between matched objects) and

that

sometimes performs

in ways users don't

expect. (i.e. all combinations

of

objects that match

the conditions are

affected by the rule)
2) Can you add a property to

the Charge

object?  Then

you could use a

boolean named

"applied" to

prevent future

matches.

Rule "Update Amount"
   when
      amountFact : Fact(name

==

"Amount")

      charge : Charge(applied

== false)

   then
      Double amount =

amountFact.getAmount();

      Double chargeAmount =

charge.getAmount();

amountFact.setAmount(amount +

chargeAmount);

      update(amountFact);
      charge.setApplied(true);
      update(charge);
end

If a charge could be applied

to multiple

Facts you

could maintain an

"appliedTo" list of

Facts in

the Charge, and

check that instead of a

simple boolean.

--- On Tue, 11/4/08, Dan

Seaver

<dan.seaver@ge.com> wrote:

From: Dan Seaver

<dan.seaver@ge.com>

Subject: [rules-users]

Chart

notation, update, and

infinite loops

To:

rules-users@lists.jboss.org

Date: Tuesday, November 4,

2008,

11:50 AM

I'm trying to find a

good

technique for

updating

specific facts in working
memory. What I'm

currently doing

is something

like

this:

Rule "Update

Amount"

   when
      amountFact :

Fact(name ==

"Amount")

      charge : Charge()
   then
      Double amount =

amountFact.getAmount();

      Double chargeAmount

=

charge.getAmount();

amountFact.setAmount(amount +

chargeAmount);

      update(amountFact);
end

The update statement

causes an

infinite loop.

I tried using no-loop,

which works

if there is 1

charge,

but not if there
are more than one.

Any help with solutions or

strategies would be

much

appreciated.
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--
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com

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