If the Quantity and Duration object already exist in your application, can they
be inserted into working memory automatically? (i.e. their existence can be
assumed when writing the rules.)
Another option is to get them using the from keyword and an external method
that generates objects. (Or optionally gets them from a map if they've alreay
been created.)
rule "foo"
when
$quantity : Quantity() from getQuantity(2, "m");
$Person($height > $quantity.height)
then
...
end
I'm not completely sure that syntax will work as written, but you get the idea.
And, not to go too far into a philosophy discussion, but the domain expert
should not be writing DRL directly if they're a non-programmer. Actually,
domain experts should not be writing rules at all. That's the job of the
knowledge engineer. There are many complexities to consider when authoring
rules. If a domain expert is stymied by something as simple as initializing
the working memory properly they're going to have a steep learning curve.
--- On Wed, 2/25/09, David Boaz <dav...@dbmotion.com> wrote:
> From: David Boaz <dav...@dbmotion.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: rules-users@lists.jboss.org
> Date: Wednesday, February 25, 2009, 1:02 PM
> Thanks,
> These Quantity and Duration objects are commonly used in
> our application. My
> concern is from the software-engineering prespective. Now,
> the rule author
> (which is supposed to be a "domain expert") has
> to maintain the information
> twice: once when inserting these objects to the working
> memory (at the
> initialization), and then when writing the concrete rules.
> Im looking for a trick to make the rule-aurhor life more
> convienient...
>
> Greg Barton wrote:
> >
> > I'd second this idea, and to get around the
> inconcenience of inserting the
> > Quantity objects from the calling application, use a
> rule that fires once
> > on initialization.
> >
> > rule
> > no-loop true
> > when
> > //No condition
> > then
> > insert(new Quantity("m", 2));
> > end
> >
> > This rule should fire first. You could also put it in
> it's own
> > agenda-group (call it "initialization" or
> some such) and set focus to that
> > group when starting.
> >
> > rule
> > agenda-group "initialization"
> > no-loop true
> > when
> > //No condition
> > then
> > insert(new Quantity("m", 2));
> >
> drools.setFocus("whatever_your_next_group_is");
> > end
> >
> > --- On Wed, 2/25/09, Mauricio Salatino
> <sala...@gmail.com> wrote:
> >
> >> From: Mauricio Salatino <sala...@gmail.com>
> >> Subject: Re: [rules-users] Creating objects in
> WHEN clause
> >> To: "Rules Users List"
> <rules-users@lists.jboss.org>
> >> Date: Wednesday, February 25, 2009, 11:40 AM
> >> How about :
> >> WHEN
> >> $quantity: Quantity(value == 2, unit ==
> "m")
> >> $Person($height == $quantity:)
> >> then
> >> ...
> >>
> >>
> >>
> >> On Wed, Feb 25, 2009 at 2:27 PM, David Boaz
> >> <dav...@dbmotion.com> wrote:
> >> >
> >> > In my application, we often compare the
> fact's
> >> field values against a known
> >> > object. For example:
> >> > WHEN person(height> new Quantity(2,
> "m"))
> >> // the height is greater than 2
> >> > meters.
> >> > will DROOLS create a "singleton"
> Quantity
> >> object, or will it create one
> >> > object for each fact evaluation?
> >> >
> >> > We consider using anoter approach, using
> GLOBALS.
> >> Then, the Quantity object
> >> > will be created applicatively, and passed by
> the API
> >> to the engine.
> >> > something like:
> >> > GLOBAL Quantity 2meters
> >> > WHEN person(height > 2meters)
> >> > But this approach is combersom, because the
> rule
> >> author has to define part
> >> > of the information in the calling
> application, and
> >> part in the rule.
> >> >
> >> > Do you have a good practice how to handle
> these
> >> situations?
> >> >
> >> > Thanks, David
> >> > --
> >> > View this message in context:
> >>
> http://www.nabble.com/Creating-objects-in-WHEN-clause-tp22207616p22207616.html
> >> > Sent from the drools - user mailing list
> archive at
> >> Nabble.com.
> >> >
> >> >
> _______________________________________________
> >> > rules-users mailing list
> >> > rules-users@lists.jboss.org
> >> >
> https://lists.jboss.org/mailman/listinfo/rules-users
> >> >
> >>
> >>
> >>
> >> --
> >> - Salatino Mauricio -
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users@lists.jboss.org
> >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users@lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
> --
> View this message in context:
> http://www.nabble.com/Creating-objects-in-WHEN-clause-tp22207616p22209417.html
> Sent from the drools - user mailing list archive at
> Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users@lists.jboss.org
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