11:27 a.m.
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...
Sent from the drools - user mailing list archive at Nabble.com.
11:40 a.m.
How about :
WHEN
$quantity: Quantity(value == 2, unit == "m")
$Person($height == $quantity:)
then
...
On Wed, Feb 25, 2009 at 2:27 PM, David Boaz <davidb(a)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...
Sent from the drools - user mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
- Salatino Mauricio -
12:05 p.m.
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 <salaboy(a)gmail.com> wrote:
From: Mauricio Salatino <salaboy(a)gmail.com>
Subject: Re: [rules-users] Creating objects in WHEN clause
To: "Rules Users List" <rules-users(a)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
<davidb(a)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...
> Sent from the drools - user mailing list archive at
Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
- Salatino Mauricio -
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
1:02 p.m.
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 <salaboy(a)gmail.com> wrote:
> From: Mauricio Salatino <salaboy(a)gmail.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: "Rules Users List" <rules-users(a)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
> <davidb(a)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...
> > Sent from the drools - user mailing list archive at
> Nabble.com.
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
> - Salatino Mauricio -
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)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...
Sent from the drools - user mailing list archive at Nabble.com.
1:26 p.m.
Have u considered using DSLs? They can hide the object model from the users
quite well.
On Wed, Feb 25, 2009 at 2:02 PM, David Boaz <davidb(a)dbmotion.com> wrote:
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 <salaboy(a)gmail.com> wrote:
>
>> From: Mauricio Salatino <salaboy(a)gmail.com>
>> Subject: Re: [rules-users] Creating objects in WHEN clause
>> To: "Rules Users List" <rules-users(a)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
>> <davidb(a)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...
>> > Sent from the drools - user mailing list archive at
>> Nabble.com.
>> >
>> > _______________________________________________
>> > rules-users mailing list
>> > rules-users(a)lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>>
>>
>>
>> --
>> - Salatino Mauricio -
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)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...
Sent from the drools - user mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
2:31 p.m.
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 <davidb(a)dbmotion.com> wrote:
From: David Boaz <davidb(a)dbmotion.com>
Subject: Re: [rules-users] Creating objects in WHEN clause
To: rules-users(a)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
<salaboy(a)gmail.com> wrote:
>
>> From: Mauricio Salatino <salaboy(a)gmail.com>
>> Subject: Re: [rules-users] Creating objects in
WHEN clause
>> To: "Rules Users List"
<rules-users(a)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
>> <davidb(a)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...
>> > Sent from the drools - user mailing list
archive at
>> Nabble.com.
>> >
>> >
_______________________________________________
>> > rules-users mailing list
>> > rules-users(a)lists.jboss.org
>> >
https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>>
>>
>>
>> --
>> - Salatino Mauricio -
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)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...
Sent from the drools - user mailing list archive at
Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
9:13 a.m.
Thanks for your all help.
with your help, my rule looks now as:
WHEN $meter:UoM( ) from UoMs.get("length","m")
$2m:Quantity() from Quantities.get(2,$meter)
Person( height < $2m )
My Quantity class implements Comparable interface. When running the rule on
a good dataset (where I expect the rule to fire), the rule fails with no
error. in addition, the compareTo(Object o) method is not called (the
debugger doesn't stop in this method).
Can you please help?
Thanks, David
Greg Barton wrote:
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 <davidb(a)dbmotion.com> wrote:
> From: David Boaz <davidb(a)dbmotion.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: rules-users(a)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
> <salaboy(a)gmail.com> wrote:
> >
> >> From: Mauricio Salatino <salaboy(a)gmail.com>
> >> Subject: Re: [rules-users] Creating objects in
> WHEN clause
> >> To: "Rules Users List"
> <rules-users(a)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
> >> <davidb(a)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...
> >> > Sent from the drools - user mailing list
> archive at
> >> Nabble.com.
> >> >
> >> >
> _______________________________________________
> >> > rules-users mailing list
> >> > rules-users(a)lists.jboss.org
> >> >
> https://lists.jboss.org/mailman/listinfo/rules-users
> >> >
> >>
> >>
> >>
> >> --
> >> - Salatino Mauricio -
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users(a)lists.jboss.org
> >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)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...
> Sent from the drools - user mailing list archive at
> Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
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http://www.nabble.com/Creating-objects-in-WHEN-clause-tp22207616p22226197...
Sent from the drools - user mailing list archive at Nabble.com.
9:54 a.m.
The problem is the "Person( height < $2m )" part. There is no operator
overloading in java, so the "<" operator must act on a numerical primitive.
(int, double, etc.) $2m is a Quantity. As for why this doesn't error out, I'm
not sure, but it certainly won't execute. (Unless mvel has some capabilities I'm
not aware of.)
Try
Person( height < $2m.height )
...as long as Person.height and Quantity.height are both numerical types.
If you want to specifically call compareTo() you should use an eval block:
WHEN
$meter:UoM( ) from UoMs.get("length","m")
$2m:Quantity() from Quantities.get(2,$meter)
$p: Person()
eval($p.getHeight().compareTo($2m))
However, even if this works, I hope you're not going to be putting too much data
through rules like this. The way it's currently constructed it completely circumvents
all of drools' indexing ability. :) The power of rules comes from tracking the
changes in a set of objects, and firing rules based on only the changes observed. (That
set is the working memory.) The "from" keyword allows you to have rules that
draw objects from outside working memory, but you pay for that convenience: the cost is
not being able to track changes. As a result, objects gathered using "from"
must be reconsidered even if they haven't changed (i.e. every time the condition is
encountered) because drools has no way of knowing if they've changed or not.
So, after this long winded spiel, here's my suggestion: get the rule(s) to work using
"from" but also try inserting the Quantity object in working memory. If
you're processing enough data with the rules you will notice a difference.
--- On Thu, 2/26/09, David Boaz <davidb(a)dbmotion.com> wrote:
From: David Boaz <davidb(a)dbmotion.com>
Subject: Re: [rules-users] Creating objects in WHEN clause
To: rules-users(a)lists.jboss.org
Date: Thursday, February 26, 2009, 9:13 AM
Thanks for your all help.
with your help, my rule looks now as:
WHEN $meter:UoM( ) from
UoMs.get("length","m")
$2m:Quantity() from Quantities.get(2,$meter)
Person( height < $2m )
My Quantity class implements Comparable interface. When
running the rule on
a good dataset (where I expect the rule to fire), the rule
fails with no
error. in addition, the compareTo(Object o) method is not
called (the
debugger doesn't stop in this method).
Can you please help?
Thanks, David
10:16 a.m.
Thanks for your excellent remarks and information!
I must pass through the Quantity.compareTo() method because I have to do
quantity conversion checks (e.g., 2m > 180 cm).
I understood the drawback of using FROM instead of using working memory
objects.
My goal is to make the rules easy to read and maintain. I want to avoid
defining "setup-rules" for inserting objects to WM, and other "real"
rules.
My Quantity objects are immutable value objects. just like the String
literal "abc", or a Date. My rule should behave exactly like Person(name ==
"abc")
Can I instruct Drools not to check for changes on that objects?
Im sure that Im not the first facing this issue.
Thanks again, David
Greg Barton wrote:
The problem is the "Person( height < $2m )" part. There is no operator
overloading in java, so the "<" operator must act on a numerical
primitive. (int, double, etc.) $2m is a Quantity. As for why this
doesn't error out, I'm not sure, but it certainly won't execute. (Unless
mvel has some capabilities I'm not aware of.)
Try
Person( height < $2m.height )
...as long as Person.height and Quantity.height are both numerical types.
If you want to specifically call compareTo() you should use an eval block:
WHEN
$meter:UoM( ) from UoMs.get("length","m")
$2m:Quantity() from Quantities.get(2,$meter)
$p: Person()
eval($p.getHeight().compareTo($2m))
However, even if this works, I hope you're not going to be putting too
much data through rules like this. The way it's currently constructed it
completely circumvents all of drools' indexing ability. :) The power of
rules comes from tracking the changes in a set of objects, and firing
rules based on only the changes observed. (That set is the working
memory.) The "from" keyword allows you to have rules that draw objects
from outside working memory, but you pay for that convenience: the cost is
not being able to track changes. As a result, objects gathered using
"from" must be reconsidered even if they haven't changed (i.e. every time
the condition is encountered) because drools has no way of knowing if
they've changed or not.
So, after this long winded spiel, here's my suggestion: get the rule(s) to
work using "from" but also try inserting the Quantity object in working
memory. If you're processing enough data with the rules you will notice a
difference.
--- On Thu, 2/26/09, David Boaz <davidb(a)dbmotion.com> wrote:
> From: David Boaz <davidb(a)dbmotion.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: rules-users(a)lists.jboss.org
> Date: Thursday, February 26, 2009, 9:13 AM
> Thanks for your all help.
> with your help, my rule looks now as:
> WHEN $meter:UoM( ) from
> UoMs.get("length","m")
> $2m:Quantity() from Quantities.get(2,$meter)
> Person( height < $2m )
>
> My Quantity class implements Comparable interface. When
> running the rule on
> a good dataset (where I expect the rule to fire), the rule
> fails with no
> error. in addition, the compareTo(Object o) method is not
> called (the
> debugger doesn't stop in this method).
>
> Can you please help?
> Thanks, David
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11:01 a.m.
--- On Thu, 2/26/09, David Boaz <davidb(a)dbmotion.com> wrote:
My Quantity objects are immutable value objects. just like
the String literal "abc", or a Date. My rule should behave
exactly like Person(name == "abc")
You should look into defining a domain specific language, as has been suggested earlier.
Can I instruct Drools not to check for changes on that
objects?
Not if you're getting them using "from". Every time it produces output it
is assumed to be fresh. The way you tell drools "this object will only change when I
tell you it's changed" is to insert it into working memory. That's it.
That's why it is there. I can't say it any plainer.
Look at it this way: say you specified that an object of type A is immutable. When it
returns from "from" you still have to check if you've seen that particular
instance before, and then if you've previously matched it with the other objects in
the rule. Checking if you've seen them before means you have to maintain a memory of
that object type, thus specifying how long you want to track each instance of that type.
It's working memory, just in another form.
Im sure that Im not the first facing this issue.
Nope. "This issue" is the reason the rete algorithm was invented. :)
I reeeeeeally don't think inserting the Quantity objects into working memory will be
as painful as you think. It can probably be handled behind the scenes without
intervention from the rule writer.
12:46 p.m.
Just a comment:
"There is no operator overloading in java, so the "<" operator must act
on a
numerical primitive. (int, double, etc.) "
This is not true. Comparison operators will work on any "comparable"
type. So if Quantity implements Comparable interface, it must work.
Otherwise it is a bug.
Although, remember that Drools always makes type coercion from the right
to the left value, so, for that to actually work:
Person( height < $2m )
"height" must be comparable to $2m.
[]s
Edson
2009/2/26 Greg Barton <greg_barton(a)yahoo.com>
The problem is the "Person( height < $2m )" part. There
is no operator
overloading in java, so the "<" operator must act on a numerical primitive.
(int, double, etc.) $2m is a Quantity. As for why this doesn't error out,
I'm not sure, but it certainly won't execute. (Unless mvel has some
capabilities I'm not aware of.)
Try
Person( height < $2m.height )
...as long as Person.height and Quantity.height are both numerical types.
If you want to specifically call compareTo() you should use an eval block:
WHEN
$meter:UoM( ) from UoMs.get("length","m")
$2m:Quantity() from Quantities.get(2,$meter)
$p: Person()
eval($p.getHeight().compareTo($2m))
However, even if this works, I hope you're not going to be putting too much
data through rules like this. The way it's currently constructed it
completely circumvents all of drools' indexing ability. :) The power of
rules comes from tracking the changes in a set of objects, and firing rules
based on only the changes observed. (That set is the working memory.) The
"from" keyword allows you to have rules that draw objects from outside
working memory, but you pay for that convenience: the cost is not being able
to track changes. As a result, objects gathered using "from" must be
reconsidered even if they haven't changed (i.e. every time the condition is
encountered) because drools has no way of knowing if they've changed or not.
So, after this long winded spiel, here's my suggestion: get the rule(s) to
work using "from" but also try inserting the Quantity object in working
memory. If you're processing enough data with the rules you will notice a
difference.
--- On Thu, 2/26/09, David Boaz <davidb(a)dbmotion.com> wrote:
> From: David Boaz <davidb(a)dbmotion.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: rules-users(a)lists.jboss.org
> Date: Thursday, February 26, 2009, 9:13 AM
> Thanks for your all help.
> with your help, my rule looks now as:
> WHEN $meter:UoM( ) from
> UoMs.get("length","m")
> $2m:Quantity() from Quantities.get(2,$meter)
> Person( height < $2m )
>
> My Quantity class implements Comparable interface. When
> running the rule on
> a good dataset (where I expect the rule to fire), the rule
> fails with no
> error. in addition, the compareTo(Object o) method is not
> called (the
> debugger doesn't stop in this method).
>
> Can you please help?
> Thanks, David
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
3:42 p.m.
Oh, you dun thrown down the gauntlet now. :)
The following will not compile with java6:
public class ComparableFu {
static class Foo implements Comparable<Foo> {
private int foo;
public Foo(int foo) {
this.foo = foo;
}
public int compareTo(Foo other) {
if(other.foo < foo) {
return -1;
} else if(other.foo == foo) {
return 0;
} else {
return 1;
}
}
}
public static void main(String[] args) {
System.out.println(new Foo(1) < new Foo(2)); //Baaaaad!
}
}
Methinks the overloading of comparison operators for Comparables is an mvel feature.
--- On Sun, 3/1/09, Edson Tirelli <tirelli(a)post.com> wrote:
From: Edson Tirelli <tirelli(a)post.com>
Subject: Re: [rules-users] Creating objects in WHEN clause
To: greg_barton(a)yahoo.com, "Rules Users List"
<rules-users(a)lists.jboss.org>
Date: Sunday, March 1, 2009, 12:46 PM
Just a comment:
"There is no operator overloading in java, so the
"<" operator must act on a
numerical primitive. (int, double, etc.) "
This is not true. Comparison operators will work on any
"comparable"
type. So if Quantity implements Comparable interface, it
must work.
Otherwise it is a bug.
Although, remember that Drools always makes type
coercion from the right
to the left value, so, for that to actually work:
Person( height < $2m )
"height" must be comparable to $2m.
[]s
Edson
2009/2/26 Greg Barton <greg_barton(a)yahoo.com>
> The problem is the "Person( height < $2m
)" part. There is no operator
> overloading in java, so the "<" operator
must act on a numerical primitive.
> (int, double, etc.) $2m is a Quantity. As for why
this doesn't error out,
> I'm not sure, but it certainly won't execute.
(Unless mvel has some
> capabilities I'm not aware of.)
>
> Try
>
> Person( height < $2m.height )
>
> ...as long as Person.height and Quantity.height are
both numerical types.
>
> If you want to specifically call compareTo() you
should use an eval block:
>
> WHEN
> $meter:UoM( ) from
UoMs.get("length","m")
> $2m:Quantity() from Quantities.get(2,$meter)
> $p: Person()
> eval($p.getHeight().compareTo($2m))
>
> However, even if this works, I hope you're not
going to be putting too much
> data through rules like this. The way it's
currently constructed it
> completely circumvents all of drools' indexing
ability. :) The power of
> rules comes from tracking the changes in a set of
objects, and firing rules
> based on only the changes observed. (That set is the
working memory.) The
> "from" keyword allows you to have rules that
draw objects from outside
> working memory, but you pay for that convenience: the
cost is not being able
> to track changes. As a result, objects gathered using
"from" must be
> reconsidered even if they haven't changed (i.e.
every time the condition is
> encountered) because drools has no way of knowing if
they've changed or not.
>
> So, after this long winded spiel, here's my
suggestion: get the rule(s) to
> work using "from" but also try inserting the
Quantity object in working
> memory. If you're processing enough data with the
rules you will notice a
> difference.
>
> --- On Thu, 2/26/09, David Boaz
<davidb(a)dbmotion.com> wrote:
>
> > From: David Boaz <davidb(a)dbmotion.com>
> > Subject: Re: [rules-users] Creating objects in
WHEN clause
> > To: rules-users(a)lists.jboss.org
> > Date: Thursday, February 26, 2009, 9:13 AM
> > Thanks for your all help.
> > with your help, my rule looks now as:
> > WHEN $meter:UoM( ) from
> > UoMs.get("length","m")
> > $2m:Quantity() from
Quantities.get(2,$meter)
> > Person( height < $2m )
> >
> > My Quantity class implements Comparable
interface. When
> > running the rule on
> > a good dataset (where I expect the rule to fire),
the rule
> > fails with no
> > error. in addition, the compareTo(Object o)
method is not
> > called (the
> > debugger doesn't stop in this method).
> >
> > Can you please help?
> > Thanks, David
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
3:42 a.m.
Thanks Edson,
Indeed my Quantity class implements Comparable, and the described problem
was mysteriously solved. So, the expression Person( height < $2m ) does
work. BTW, this feature is not documented in "drools-docs-expert.pdf".
David
Edson Tirelli-3 wrote:
Just a comment:
"There is no operator overloading in java, so the "<" operator must act
on
a
numerical primitive. (int, double, etc.) "
This is not true. Comparison operators will work on any "comparable"
type. So if Quantity implements Comparable interface, it must work.
Otherwise it is a bug.
Although, remember that Drools always makes type coercion from the
right
to the left value, so, for that to actually work:
Person( height < $2m )
"height" must be comparable to $2m.
[]s
Edson
2009/2/26 Greg Barton <greg_barton(a)yahoo.com>
> The problem is the "Person( height < $2m )" part. There is no operator
> overloading in java, so the "<" operator must act on a numerical
> primitive.
> (int, double, etc.) $2m is a Quantity. As for why this doesn't error
> out,
> I'm not sure, but it certainly won't execute. (Unless mvel has some
> capabilities I'm not aware of.)
>
> Try
>
> Person( height < $2m.height )
>
> ...as long as Person.height and Quantity.height are both numerical types.
>
> If you want to specifically call compareTo() you should use an eval
> block:
>
> WHEN
> $meter:UoM( ) from UoMs.get("length","m")
> $2m:Quantity() from Quantities.get(2,$meter)
> $p: Person()
> eval($p.getHeight().compareTo($2m))
>
> However, even if this works, I hope you're not going to be putting too
> much
> data through rules like this. The way it's currently constructed it
> completely circumvents all of drools' indexing ability. :) The power of
> rules comes from tracking the changes in a set of objects, and firing
> rules
> based on only the changes observed. (That set is the working memory.)
> The
> "from" keyword allows you to have rules that draw objects from outside
> working memory, but you pay for that convenience: the cost is not being
> able
> to track changes. As a result, objects gathered using "from" must be
> reconsidered even if they haven't changed (i.e. every time the condition
> is
> encountered) because drools has no way of knowing if they've changed or
> not.
>
> So, after this long winded spiel, here's my suggestion: get the rule(s)
> to
> work using "from" but also try inserting the Quantity object in working
> memory. If you're processing enough data with the rules you will notice
> a
> difference.
>
> --- On Thu, 2/26/09, David Boaz <davidb(a)dbmotion.com> wrote:
>
> > From: David Boaz <davidb(a)dbmotion.com>
> > Subject: Re: [rules-users] Creating objects in WHEN clause
> > To: rules-users(a)lists.jboss.org
> > Date: Thursday, February 26, 2009, 9:13 AM
> > Thanks for your all help.
> > with your help, my rule looks now as:
> > WHEN $meter:UoM( ) from
> > UoMs.get("length","m")
> > $2m:Quantity() from Quantities.get(2,$meter)
> > Person( height < $2m )
> >
> > My Quantity class implements Comparable interface. When
> > running the rule on
> > a good dataset (where I expect the rule to fire), the rule
> > fails with no
> > error. in addition, the compareTo(Object o) method is not
> > called (the
> > debugger doesn't stop in this method).
> >
> > Can you please help?
> > Thanks, David
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
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5:03 a.m.
Thanks Greg,
I tried to apply your solution proposed bellow, but had problem setting the
initial "agenda-group". I'm using Drools 5.0.0.M4 version, and working with
a StatelessSession API.
Can you please give an example how to set the initial "agenda-group" from
the StatelessSession API?
BTW, regarding the discussion we had, whether to use FROM or WorkingMemory
objects, is it applicable also when using a stateless session?
Thanks, David
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 <salaboy(a)gmail.com> wrote:
> From: Mauricio Salatino <salaboy(a)gmail.com>
> Subject: Re: [rules-users] Creating objects in WHEN clause
> To: "Rules Users List" <rules-users(a)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
> <davidb(a)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...
> > Sent from the drools - user mailing list archive at
> Nabble.com.
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
> - Salatino Mauricio -
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
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12:17 p.m.
Well, since the StatelessSession is basically a convenience wrapper around a
StatefulSession I figure it should be possible. On StatefulSession, which extends
WorkingMemory, you just call setFocus() before firing the rules. I'm not sure what
the best way to do this with a StatelessSession would be. I can think of some hacks, but
would rather not lead you down a garden path. :) Dev d00ds, any comment?
--- On Sun, 3/1/09, David Boaz <davidb(a)dbmotion.com> wrote:
From: David Boaz <davidb(a)dbmotion.com>
Subject: Re: [rules-users] Creating objects in WHEN clause
To: rules-users(a)lists.jboss.org
Date: Sunday, March 1, 2009, 5:03 AM
Thanks Greg,
I tried to apply your solution proposed bellow, but had
problem setting the
initial "agenda-group". I'm using Drools
5.0.0.M4 version, and working with
a StatelessSession API.
Can you please give an example how to set the initial
"agenda-group" from
the StatelessSession API?
BTW, regarding the discussion we had, whether to use FROM
or WorkingMemory
objects, is it applicable also when using a stateless
session?
Thanks, David
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
<salaboy(a)gmail.com> wrote:
>
>> From: Mauricio Salatino <salaboy(a)gmail.com>
>> Subject: Re: [rules-users] Creating objects in
WHEN clause
>> To: "Rules Users List"
<rules-users(a)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
>> <davidb(a)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...
>> > Sent from the drools - user mailing list
archive at
>> Nabble.com.
>> >
>> >
_______________________________________________
>> > rules-users mailing list
>> > rules-users(a)lists.jboss.org
>> >
https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>>
>>
>>
>> --
>> - Salatino Mauricio -
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
--
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Nabble.com.
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6261
days inactive
6267
days old
14 comments
5 participants
participants (5)
-
David Boaz -
David Sinclair -
Edson Tirelli -
Greg Barton -
Mauricio Salatino