1:30 a.m.
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
4:24 a.m.
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
4:51 a.m.
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
7:28 a.m.
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules independent of each
other to the maximal degree to which that is possible. That's why I didn' t want
to have isZombie==false in the general rule - I wanted the general case to be unaware of
the exceptions. The field in which I'm working is clinical decision support where
there might be a number of exceptions and corner cases. I'd like to be able to
express the core logic without reference to the corner cases and then deal with the
exceptions separately.
I think your idea of using salience but only adding advice if it hasn't already been
given fits the bill - that way the general case can be simple and not have to explicitly
exclude all the exception cases.
Thanks very much for the feedback - it's really valuable to get an idea about what
options are available and what's considered best practice.
Cheers!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of David Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
8:58 a.m.
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use
of "null advice", such that:-
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
insertLogical( new Diagnosis( $p ) );
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Evidence suggests that the undead cannot contract
Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
*
*
*end*
As David states, more specific rules should have higher salience than the
more general that should have lower. Salience controls conflict resolution,
which is the order in which activations on the agenda are evaluated, it does
not control which rules are evaluated - which happens as facts are inserted
into working memory and not when fireAllRules( ) invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules
independent of each other to the maximal degree to which that is possible.
That’s why I didn’ t want to have isZombie==false in the general rule – I
wanted the general case to be unaware of the exceptions. The field in which
I’m working is clinical decision support where there might be a number of
exceptions and corner cases. I’d like to be able to express the core logic
without reference to the corner cases and then deal with the exceptions
separately.
I think your idea of using salience but only adding advice if it hasn’t
already been given fits the bill – that way the general case can be simple
and not have to explicitly exclude all the exception cases.
Thanks very much for the feedback – it’s really valuable to get an idea
about what options are available and what’s considered best practice.
Cheers!
Peter.
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *David Faulkner
*Sent:* Wednesday, 9 March 2011 4:51 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
“activation-group”; if two rules are in the same activation group, only one
of them will fire. Note that the rule with HIGHER salience will fire first;
to accomplish what you are looking for you’d have to give the exception rule
a higher salience.
I would also note that although there are specific instances where
activation-group has a strong need, many in the community find that the most
power and flexibility from the rule engine comes from “letting go” of trying
to exactly order your rule execution, and instead letting the rule engine
decide what would happen here. One way to accomplish this in your case would
be to simply add (isZombie == false) to your constraint on the general rule.
Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The
possibilities are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Peter Ashford
*Sent:* Wednesday, March 09, 2011 7:24 AM
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Actually, I think I’ve figured this one out : in the Zombie case, it’s
firing both rules and it’s just that with the negative salience, the zombie
exception rule is the last rule fired, therefore, the last thing written
into advice.
So... what would be the correct way to do what I’m trying to do here? The
idea is that the Zombie exception rule should fire in preference to the
general rule and that none of the general processing should occur at all
(imaging that these rules had side-effects for the rest of the system
they’re attached to, we don’t want all the general rule side effects to
apply and then all the exception case side effects)
Thanks in advance!
Peter.
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Peter Ashford
*Sent:* Wednesday, 9 March 2011 1:31 p.m.
*To:* rules-users(a)lists.jboss.org
*Subject:* [rules-users] Misunderstanding salience?
Hi There
I’m new to drools. I’ve just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that’s not working as I
expect it is the rule ordering via salience. This is my simple test rule
set:
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
*end*
The idea is that the first rule fires all the time unless the patient
happens to be a zombie, in which case the exception rule (the second rule)
kicks in. Now, as I have it here, with the exception at salience at -50 it
actually works, which is the opposite of what I was expecting. I’d thought
that I would have had to have the exception at a higher salience to fire
first. That was what I tried first but that didn’t work – everyone got the
general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
“It is very difficult to get a man to understand something when his tribal
identity depends on his not understanding it” - Michael Bérubé on
Republican climate change denial.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
10:23 a.m.
I don't think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time - if not control facts would
have to be the way to go.
You also need to make sure you actually tell the rule engine you have modified the patient
when you set their advice - you need to wrap the call with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: 09 March 2011 07:58
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use of "null
advice", such that:-
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
insertLogical( new Diagnosis( $p ) );
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
end
As David states, more specific rules should have higher salience than the more general
that should have lower. Salience controls conflict resolution, which is the order in which
activations on the agenda are evaluated, it does not control which rules are evaluated -
which happens as facts are inserted into working memory and not when fireAllRules( )
invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford
<petera@bestpractice.org.nz<mailto:petera@bestpractice.org.nz>>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules independent of each
other to the maximal degree to which that is possible. That's why I didn' t want
to have isZombie==false in the general rule - I wanted the general case to be unaware of
the exceptions. The field in which I'm working is clinical decision support where
there might be a number of exceptions and corner cases. I'd like to be able to
express the core logic without reference to the corner cases and then deal with the
exceptions separately.
I think your idea of using salience but only adding advice if it hasn't already been
given fits the bill - that way the general case can be simple and not have to explicitly
exclude all the exception cases.
Thanks very much for the feedback - it's really valuable to get an idea about what
options are available and what's considered best practice.
Cheers!
Peter.
From:
rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>]
On Behalf Of David Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner@amentra.com<mailto:david.faulkner@amentra.com>
From:
rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>]
On Behalf Of Peter Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From:
rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org<mailto:rules-users-bounces@lists.jboss.org>]
On Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users@lists.jboss.org<mailto:rules-users@lists.jboss.org>
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org<mailto:rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
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9:54 p.m.
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the decision.
Usually that's an emergency case and it will be something like "this patient
needs to be admitted to hospital immediately". In other cases, we want to provide
some advice which a clinician may or may not choose to heed. It sounds to me that the
insertLogical mechanism might well work for those latter cases (was this what you were
referring to when you talked about 'control facts'?) In the other case - an
emergency when you need to give one element of critical advice then quit - is there an
option to terminate the rules immediately and return the current result?
Peter
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Swindells, Thomas
Sent: Wednesday, 9 March 2011 10:23 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
I don't think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time - if not control facts would
have to be the way to go.
You also need to make sure you actually tell the rule engine you have modified the patient
when you set their advice - you need to wrap the call with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: 09 March 2011 07:58
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use of "null
advice", such that:-
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
insertLogical( new Diagnosis( $p ) );
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
end
As David states, more specific rules should have higher salience than the more general
that should have lower. Salience controls conflict resolution, which is the order in which
activations on the agenda are evaluated, it does not control which rules are evaluated -
which happens as facts are inserted into working memory and not when fireAllRules( )
invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules independent of each
other to the maximal degree to which that is possible. That's why I didn' t want
to have isZombie==false in the general rule - I wanted the general case to be unaware of
the exceptions. The field in which I'm working is clinical decision support where
there might be a number of exceptions and corner cases. I'd like to be able to
express the core logic without reference to the corner cases and then deal with the
exceptions separately.
I think your idea of using salience but only adding advice if it hasn't already been
given fits the bill - that way the general case can be simple and not have to explicitly
exclude all the exception cases.
Thanks very much for the feedback - it's really valuable to get an idea about what
options are available and what's considered best practice.
Cheers!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of David Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
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https://lists.jboss.org/mailman/listinfo/rules-users
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10:30 p.m.
"Control facts" is a term for objects in working memory that are not directly
derived from outside data, or used as output. As their name implies, they're used to
explicitly control flow of the rules.
--- On Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz> wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients.... A wrinkle we have is that
sometimes an exception case should terminate the decision. Usually that’s an emergency
case and it will be something like “this patient needs to be admitted to hospital
immediately”. In other cases, we want to provide some advice which a clinician may or may
not choose to heed. It sounds to me that the insertLogical mechanism might well work for
those latter cases (was this what you were referring to when you talked about ‘control
facts’?) In the other case – an emergency when you need to give one element of critical
advice then quit – is there an option to terminate the rules immediately and return the
current result? Peter From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Swindells, Thomas
Sent: Wednesday, 9 March 2011 10:23 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience? I don’t think you even need it that
complicated.Just have your constraints in the form Patient(advice == null, ...) This
assumes you only give the patient one advice at a time – if not control facts would have
to be the way to go. You also need to make sure you actually tell the rule engine you have
modified the patient when you set their advice – you need to wrap the call with a
modify(p) {...}. Hope you get your zombies under control soon, Thomas From:
rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf
Of Michael Anstis
Sent: 09 March 2011 07:58
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience? You had me fooled Peter, I thought
you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use of "null
advice", such that:-rule "General brain eating advice"
when p : Patient(eatsBrains == true) not Diagnosis(
patient == $p ) then p.setAdvice("Stop eating brains, or at least,
try to cut down"); insertLogical( new Diagnosis( $p ) ); end rule
"Zombie exception to brain eating advice" salience -50
when p : Patient(eatsBrains == true, isZombie == true)
not Diagnosis( patient == $p ) then p.setAdvice("Evidence suggests
that the undead cannot contract Kuru or that the effects are irellevant given the "
+ "patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains"); insertLogical( new
Diagnosis( $p ) ); end
As David states, more specific rules should have higher salience than the more general
that should have lower. Salience controls conflict resolution, which is the order in which
activations on the agenda are evaluated, it does not control which rules are evaluated -
which happens as facts are inserted into working memory and not when fireAllRules( )
invoked.
With kind regards,
Mike2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>Thanks for the ideas,
David. What I ultimately want to achieve is to have the individual rules independent of
each other to the maximal degree to which that is possible. That’s why I didn’ t want to
have isZombie==false in the general rule – I wanted the general case to be unaware of the
exceptions. The field in which I’m working is clinical decision support where there might
be a number of exceptions and corner cases. I’d like to be able to express the core logic
without reference to the corner cases and then deal with the exceptions separately. I
think your idea of using salience but only adding advice if it hasn’t already been given
fits the bill – that way the general case can be simple and not have to explicitly exclude
all the exception cases. Thanks very much for the feedback – it’s really valuable to get
an idea about what options are available and what’s
considered best practice. Cheers! Peter. From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of David Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience? Peter, The EXACT way to accomplish
the functionality that you are looking for is “activation-group”; if two rules are in the
same activation group, only one of them will fire. Note that the rule with HIGHER salience
will fire first; to accomplish what you are looking for you’d have to give the exception
rule a higher salience. I would also note that although there are specific instances where
activation-group has a strong need, many in the community find that the most power and
flexibility from the rule engine comes from “letting go” of trying to exactly order your
rule execution, and instead letting the rule engine decide what would happen here. One way
to accomplish this in your case would be to simply add (isZombie == false) to your
constraint on the general rule. Another way that involves salience but NOT agenda groups
is to set a high salience on your exception rule, but only add
advice if advice is null. The possibilities are endless. With kind regards,David
Faulknerdavid.faulkner(a)amentra.com from: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Peter Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience? Actually, I think I’ve figured this
one out : in the Zombie case, it’s firing both rules and it’s just that with the negative
salience, the zombie exception rule is the last rule fired, therefore, the last thing
written into advice. So... what would be the correct way to do what I’m trying to do here?
The idea is that the Zombie exception rule should fire in preference to the general rule
and that none of the general processing should occur at all (imaging that these rules had
side-effects for the rest of the system they’re attached to, we don’t want all the general
rule side effects to apply and then all the exception case side effects) Thanks in
advance! Peter. From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Peter Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org
Subject: [rules-users] Misunderstanding salience? Hi There I’m new to drools. I’ve just
set up the Drools-Server and it is (finally!) working and serving my test rule-set. The
one thing that’s not working as I expect it is the rule ordering via salience. This is my
simple test rule set: rule "General brain eating advice" when
p : Patient(eatsBrains == true) then p.setAdvice("Stop
eating brains, or at least, try to cut down"); end rule "Zombie exception to
brain eating advice" salience -50 when p :
Patient(eatsBrains == true, isZombie == true) then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or that the
effects are irellevant given the " + "patient's
current zombified
state.\nSuggest euthenasing patient lest he/she eat your (or someone "
+ "else's) brains"); end The idea
is that the first rule fires all the time unless the patient happens to be a zombie, in
which case the exception rule (the second rule) kicks in. Now, as I have it here, with
the exception at salience at -50 it actually works, which is the opposite of what I was
expecting. I’d thought that I would have had to have the exception at a higher salience
to fire first. That was what I tried first but that didn’t work – everyone got the
general advice, zombies included. What am I misunderstanding here? Thanks! Peter. ---“It
is very difficult to get a man to understand something when his tribal identity depends on
his not understanding it” - Michael Bérubé on Republican climate change denial.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
**************************************************************************************
This message is confidential and intended only for the addressee. If you have received
this message in error, please immediately notify the postmaster(a)nds.com and delete it from
your system as well as any copies. The content of e-mails as well as traffic data may be
monitored by NDS for employment and security purposes. To protect the environment please
do not print this e-mail unless necessary.
NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18 4EX, United
Kingdom. A company registered in England and Wales. Registered no. 3080780. VAT no. GB 603
8808 40-00
**************************************************************************************
-----Inline Attachment Follows-----
_______________________________________________
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https://lists.jboss.org/mailman/listinfo/rules-users
10:45 p.m.
I don't suppose you (Peter) use RuleFlow or jBPM?
If not then remember rules' patterns are matched as facts are inserted into
WM. The resulting activations are ordered by controlling semantics such as
salience, no-loop, lock-on-active etc. Therefore should higher salience
rules activations (that will be executed first) alter the state of WM lower
salience rules' activations could be removed (by the presence of the control
fact or non-null "advice" depending on what approach you take) and hence not
be candidate for execution.
This is why, IMO, people talk about considering all rules executing in
parallel rather than sequentially.
If you're using jBPM then fail-fast is an option, but not something I know
much about.
Cheers,
Mike
2011/3/9 Greg Barton <greg_barton(a)yahoo.com>
"Control facts" is a term for objects in working memory
that are not
directly derived from outside data, or used as output. As their name
implies, they're used to explicitly control flow of the rules.
--- On *Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz>* wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the
decision. Usually that’s an emergency case and it will be something like
“this patient needs to be admitted to hospital immediately”. In other
cases, we want to provide some advice which a clinician may or may not
choose to heed. It sounds to me that the insertLogical mechanism might well
work for those latter cases (was this what you were referring to when you
talked about ‘control facts’?) In the other case – an emergency when you
need to give one element of critical advice then quit – is there an option
to terminate the rules immediately and return the current result?
Peter
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Swindells, Thomas
*Sent:* Wednesday, 9 March 2011 10:23 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
I don’t think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time – if not
control facts would have to be the way to go.
You also need to make sure you actually tell the rule engine you have
modified the patient when you set their advice – you need to wrap the call
with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Michael Anstis
*Sent:* 09 March 2011 07:58
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use
of "null advice", such that:-
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
insertLogical( new Diagnosis( $p ) );
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
*end*
As David states, more specific rules should have higher salience than the
more general that should have lower. Salience controls conflict resolution,
which is the order in which activations on the agenda are evaluated, it does
not control which rules are evaluated - which happens as facts are inserted
into working memory and not when fireAllRules( ) invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford
<petera@bestpractice.org.nz<http://mc/compose?to=petera@bestpractice.org.nz>
>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules
independent of each other to the maximal degree to which that is possible.
That’s why I didn’ t want to have isZombie==false in the general rule – I
wanted the general case to be unaware of the exceptions. The field in which
I’m working is clinical decision support where there might be a number of
exceptions and corner cases. I’d like to be able to express the core logic
without reference to the corner cases and then deal with the exceptions
separately.
I think your idea of using salience but only adding advice if it hasn’t
already been given fits the bill – that way the general case can be simple
and not have to explicitly exclude all the exception cases.
Thanks very much for the feedback – it’s really valuable to get an idea
about what options are available and what’s considered best practice.
Cheers!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *David Faulkner
*Sent:* Wednesday, 9 March 2011 4:51 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
“activation-group”; if two rules are in the same activation group, only one
of them will fire. Note that the rule with HIGHER salience will fire first;
to accomplish what you are looking for you’d have to give the exception rule
a higher salience.
I would also note that although there are specific instances where
activation-group has a strong need, many in the community find that the most
power and flexibility from the rule engine comes from “letting go” of trying
to exactly order your rule execution, and instead letting the rule engine
decide what would happen here. One way to accomplish this in your case would
be to simply add (isZombie == false) to your constraint on the general rule.
Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The
possibilities are endless.
With kind regards,
David Faulkner
david.faulkner@amentra.com<http://mc/compose?to=david.faulkner@amentra.com>
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, March 09, 2011 7:24 AM
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Actually, I think I’ve figured this one out : in the Zombie case, it’s
firing both rules and it’s just that with the negative salience, the zombie
exception rule is the last rule fired, therefore, the last thing written
into advice.
So... what would be the correct way to do what I’m trying to do here? The
idea is that the Zombie exception rule should fire in preference to the
general rule and that none of the general processing should occur at all
(imaging that these rules had side-effects for the rest of the system
they’re attached to, we don’t want all the general rule side effects to
apply and then all the exception case side effects)
Thanks in advance!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, 9 March 2011 1:31 p.m.
*To:*
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
*Subject:* [rules-users] Misunderstanding salience?
Hi There
I’m new to drools. I’ve just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that’s not working as I
expect it is the rule ordering via salience. This is my simple test rule
set:
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
*end*
The idea is that the first rule fires all the time unless the patient
happens to be a zombie, in which case the exception rule (the second rule)
kicks in. Now, as I have it here, with the exception at salience at -50 it
actually works, which is the opposite of what I was expecting. I’d thought
that I would have had to have the exception at a higher salience to fire
first. That was what I tried first but that didn’t work – everyone got the
general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
“It is very difficult to get a man to understand something when his tribal
identity depends on his not understanding it” - Michael Bérubé on
Republican climate change denial.
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
------------------------------
**************************************************************************************
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have received this message in error, please immediately notify the
postmaster(a)nds.com and delete it from your system as well as any copies.
The content of e-mails as well as traffic data may be monitored by NDS for
employment and security purposes. To protect the environment please do not
print this e-mail unless necessary.
NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18
4EX, United Kingdom. A company registered in England and Wales. Registered
no. 3080780. VAT no. GB 603 8808 40-00
**************************************************************************************
-----Inline Attachment Follows-----
_______________________________________________
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https://lists.jboss.org/mailman/listinfo/rules-users
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11:05 p.m.
Ok, thanks. I can see how asserting a control fact would work here - I only asked about
a terminate option to be able to avoid having to check for the absence of the control fact
in every rule, but that's fine if that's what I have to do.
Thank s everyone for the help - it's been excellent and very instructive :o)
p.s.: No, I don't use RuleFlow or jBPM. We're writing DRL's by hand and
it's our expectation that we will have clinical content experts using Guvnor to author
rules once we've got our new system up and running. At this point I'm just trying
to establish what best practice for our domain ought to be.
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: Thursday, 10 March 2011 10:45 a.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
I don't suppose you (Peter) use RuleFlow or jBPM?
If not then remember rules' patterns are matched as facts are inserted into WM. The
resulting activations are ordered by controlling semantics such as salience, no-loop,
lock-on-active etc. Therefore should higher salience rules activations (that will be
executed first) alter the state of WM lower salience rules' activations could be
removed (by the presence of the control fact or non-null "advice" depending on
what approach you take) and hence not be candidate for execution.
This is why, IMO, people talk about considering all rules executing in parallel rather
than sequentially.
If you're using jBPM then fail-fast is an option, but not something I know much
about.
Cheers,
Mike
2011/3/9 Greg Barton <greg_barton(a)yahoo.com>
"Control facts" is a term for objects in working memory that are not directly
derived from outside data, or used as output. As their name implies, they're used to
explicitly control flow of the rules.
--- On Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz> wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the decision.
Usually that's an emergency case and it will be something like "this patient
needs to be admitted to hospital immediately". In other cases, we want to provide
some advice which a clinician may or may not choose to heed. It sounds to me that the
insertLogical mechanism might well work for those latter cases (was this what you were
referring to when you talked about 'control facts'?) In the other case - an
emergency when you need to give one element of critical advice then quit - is there an
option to terminate the rules immediately and return the current result?
Peter
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Swindells, Thomas
Sent: Wednesday, 9 March 2011 10:23 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
I don't think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time - if not control facts would
have to be the way to go.
You also need to make sure you actually tell the rule engine you have modified the patient
when you set their advice - you need to wrap the call with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: 09 March 2011 07:58
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use of "null
advice", such that:-
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
insertLogical( new Diagnosis( $p ) );
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
end
As David states, more specific rules should have higher salience than the more general
that should have lower. Salience controls conflict resolution, which is the order in which
activations on the agenda are evaluated, it does not control which rules are evaluated -
which happens as facts are inserted into working memory and not when fireAllRules( )
invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz
<http://mc/compose?to=petera@bestpractice.org.nz> >
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules independent of each
other to the maximal degree to which that is possible. That's why I didn' t want
to have isZombie==false in the general rule - I wanted the general case to be unaware of
the exceptions. The field in which I'm working is clinical decision support where
there might be a number of exceptions and corner cases. I'd like to be able to
express the core logic without reference to the corner cases and then deal with the
exceptions separately.
I think your idea of using salience but only adding advice if it hasn't already been
given fits the bill - that way the general case can be simple and not have to explicitly
exclude all the exception cases.
Thanks very much for the feedback - it's really valuable to get an idea about what
options are available and what's considered best practice.
Cheers!
Peter.
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of David
Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com <http://mc/compose?to=david.faulkner@amentra.com>
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of Peter
Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of Peter
Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org <http://mc/compose?to=rules-users@lists.jboss.org>
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
_______________________________________________
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8:36 a.m.
Hello Peter,
Perhaps I'm overly apprehensive, but I feel compelled to throw in a word of
warning concerning the idea of creating high salience rules for "special
cases" so as to avoid using a full set of constraints for clear separation
of the "symptom sets". Assuming (for the moment) that all symptoms are
booleans, let's say that we have to deal separately with the special cases
s1&&s2 as opposed to s1&&s2&&s3, s1, and s2. Clearly, you cannot
have them
all at the same salience level. Given that this is realistic:
- Will your "clinical content experts" be able to assign the correct set
of salience values?
- Who will validate this, and how?
Also, what if none of the "special" rules fires so that the "general
case"
kicks in but there is a set of deviations from the norm, hitherto
unobserved?
Clearly, adding all the negatives is tedious work, but that's what code
generators are there for. Using decision tables with suitable defaults would
be one way of dealing with this. I'd even investigate the implementation of
a special decision table parser/compiler for this use case.
-W
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>
Ok, thanks. I can see how asserting a control fact would work here
– I
only asked about a terminate option to be able to avoid having to check for
the absence of the control fact in every rule, but that’s fine if that’s
what I have to do.
Thank s everyone for the help – it’s been excellent and very instructive
:o)
p.s.: No, I don’t use RuleFlow or jBPM. We’re writing DRL’s by hand and
it’s our expectation that we will have clinical content experts using Guvnor
to author rules once we’ve got our new system up and running. At this point
I’m just trying to establish what best practice for our domain ought to be.
Peter.
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Michael Anstis
*Sent:* Thursday, 10 March 2011 10:45 a.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
I don't suppose you (Peter) use RuleFlow or jBPM?
If not then remember rules' patterns are matched as facts are inserted into
WM. The resulting activations are ordered by controlling semantics such as
salience, no-loop, lock-on-active etc. Therefore should higher salience
rules activations (that will be executed first) alter the state of WM lower
salience rules' activations could be removed (by the presence of the control
fact or non-null "advice" depending on what approach you take) and hence not
be candidate for execution.
This is why, IMO, people talk about considering all rules executing in
parallel rather than sequentially.
If you're using jBPM then fail-fast is an option, but not something I know
much about.
Cheers,
Mike
2011/3/9 Greg Barton <greg_barton(a)yahoo.com>
"Control facts" is a term for objects in working memory that are not
directly derived from outside data, or used as output. As their name
implies, they're used to explicitly control flow of the rules.
--- On *Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz>* wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the
decision. Usually that’s an emergency case and it will be something like
“this patient needs to be admitted to hospital immediately”. In other
cases, we want to provide some advice which a clinician may or may not
choose to heed. It sounds to me that the insertLogical mechanism might well
work for those latter cases (was this what you were referring to when you
talked about ‘control facts’?) In the other case – an emergency when you
need to give one element of critical advice then quit – is there an option
to terminate the rules immediately and return the current result?
Peter
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Swindells, Thomas
*Sent:* Wednesday, 9 March 2011 10:23 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
I don’t think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time – if not
control facts would have to be the way to go.
You also need to make sure you actually tell the rule engine you have
modified the patient when you set their advice – you need to wrap the call
with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Michael Anstis
*Sent:* 09 March 2011 07:58
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use
of "null advice", such that:-
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
insertLogical( new Diagnosis( $p ) );
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
*end*
As David states, more specific rules should have higher salience than the
more general that should have lower. Salience controls conflict resolution,
which is the order in which activations on the agenda are evaluated, it does
not control which rules are evaluated - which happens as facts are inserted
into working memory and not when fireAllRules( ) invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford
<petera@bestpractice.org.nz<http://mc/compose?to=petera@bestpractice.org.nz>
>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules
independent of each other to the maximal degree to which that is possible.
That’s why I didn’ t want to have isZombie==false in the general rule – I
wanted the general case to be unaware of the exceptions. The field in which
I’m working is clinical decision support where there might be a number of
exceptions and corner cases. I’d like to be able to express the core logic
without reference to the corner cases and then deal with the exceptions
separately.
I think your idea of using salience but only adding advice if it hasn’t
already been given fits the bill – that way the general case can be simple
and not have to explicitly exclude all the exception cases.
Thanks very much for the feedback – it’s really valuable to get an idea
about what options are available and what’s considered best practice.
Cheers!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *David Faulkner
*Sent:* Wednesday, 9 March 2011 4:51 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
“activation-group”; if two rules are in the same activation group, only one
of them will fire. Note that the rule with HIGHER salience will fire first;
to accomplish what you are looking for you’d have to give the exception rule
a higher salience.
I would also note that although there are specific instances where
activation-group has a strong need, many in the community find that the most
power and flexibility from the rule engine comes from “letting go” of trying
to exactly order your rule execution, and instead letting the rule engine
decide what would happen here. One way to accomplish this in your case would
be to simply add (isZombie == false) to your constraint on the general rule.
Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The
possibilities are endless.
With kind regards,
David Faulkner
david.faulkner@amentra.com<http://mc/compose?to=david.faulkner@amentra.com>
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, March 09, 2011 7:24 AM
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Actually, I think I’ve figured this one out : in the Zombie case, it’s
firing both rules and it’s just that with the negative salience, the zombie
exception rule is the last rule fired, therefore, the last thing written
into advice.
So... what would be the correct way to do what I’m trying to do here? The
idea is that the Zombie exception rule should fire in preference to the
general rule and that none of the general processing should occur at all
(imaging that these rules had side-effects for the rest of the system
they’re attached to, we don’t want all the general rule side effects to
apply and then all the exception case side effects)
Thanks in advance!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, 9 March 2011 1:31 p.m.
*To:*
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
*Subject:* [rules-users] Misunderstanding salience?
Hi There
I’m new to drools. I’ve just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that’s not working as I
expect it is the rule ordering via salience. This is my simple test rule
set:
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
*end*
The idea is that the first rule fires all the time unless the patient
happens to be a zombie, in which case the exception rule (the second rule)
kicks in. Now, as I have it here, with the exception at salience at -50 it
actually works, which is the opposite of what I was expecting. I’d thought
that I would have had to have the exception at a higher salience to fire
first. That was what I tried first but that didn’t work – everyone got the
general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
“It is very difficult to get a man to understand something when his tribal
identity depends on his not understanding it” - Michael Bérubé on
Republican climate change denial.
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
------------------------------
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have received this message in error, please immediately notify the
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The content of e-mails as well as traffic data may be monitored by NDS for
employment and security purposes. To protect the environment please do not
print this e-mail unless necessary.
NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18
4EX, United Kingdom. A company registered in England and Wales. Registered
no. 3080780. VAT no. GB 603 8808 40-00
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9:20 p.m.
The problem is that corner cases and exceptions are extremely numerous. You could easily
have a general case with one or two positive selectors and twenty, thirty negative
selectors. What's more, for every new corner case, every other case needs to be
updated to exclude that, which hardly seems tenable. That would lead to a huge
combination of what should be separate concerns. I'm not keen on the idea of code
generators - or rather, if I was going to go that route, I'd not even consider Drools
in the first place. We've chosen this approach because we think rules will be
readable for our content developers.
* Will your "clinical content experts" be able to assign the correct set of
salience values?
* Who will validate this, and how?
Our clinical content experts currently create decision support guidelines using Prolog,
which is basically first order logic. I think that merely prioritising rules by
comparison is a much simpler job than what they're currently doing. Validation will
most likely occur through testing, so that will be a collaboration between clinical
experts and guideline developers.
'Also, what if none of the "special" rules fires so that the "general
case" kicks in but there is a set of deviations from the norm, hitherto
unobserved?'
I don't understand. If you haven't coded for an eventuality, you'll not
capture it. This would occur whether you wrote a program to implement the decision or if
you wrote rules, surely?
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Wolfgang Laun
Sent: Thursday, 10 March 2011 8:36 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Hello Peter,
Perhaps I'm overly apprehensive, but I feel compelled to throw in a word of warning
concerning the idea of creating high salience rules for "special cases" so as to
avoid using a full set of constraints for clear separation of the "symptom
sets". Assuming (for the moment) that all symptoms are booleans, let's say that
we have to deal separately with the special cases s1&&s2 as opposed to
s1&&s2&&s3, s1, and s2. Clearly, you cannot have them all at the same
salience level. Given that this is realistic:
* Will your "clinical content experts" be able to assign the correct set of
salience values?
* Who will validate this, and how?
Also, what if none of the "special" rules fires so that the "general
case" kicks in but there is a set of deviations from the norm, hitherto unobserved?
Clearly, adding all the negatives is tedious work, but that's what code generators are
there for. Using decision tables with suitable defaults would be one way of dealing with
this. I'd even investigate the implementation of a special decision table
parser/compiler for this use case.
-W
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>
Ok, thanks. I can see how asserting a control fact would work here - I only asked about
a terminate option to be able to avoid having to check for the absence of the control fact
in every rule, but that's fine if that's what I have to do.
Thank s everyone for the help - it's been excellent and very instructive :o)
p.s.: No, I don't use RuleFlow or jBPM. We're writing DRL's by hand and
it's our expectation that we will have clinical content experts using Guvnor to author
rules once we've got our new system up and running. At this point I'm just trying
to establish what best practice for our domain ought to be.
Peter.
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: Thursday, 10 March 2011 10:45 a.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
I don't suppose you (Peter) use RuleFlow or jBPM?
If not then remember rules' patterns are matched as facts are inserted into WM. The
resulting activations are ordered by controlling semantics such as salience, no-loop,
lock-on-active etc. Therefore should higher salience rules activations (that will be
executed first) alter the state of WM lower salience rules' activations could be
removed (by the presence of the control fact or non-null "advice" depending on
what approach you take) and hence not be candidate for execution.
This is why, IMO, people talk about considering all rules executing in parallel rather
than sequentially.
If you're using jBPM then fail-fast is an option, but not something I know much
about.
Cheers,
Mike
2011/3/9 Greg Barton <greg_barton(a)yahoo.com>
"Control facts" is a term for objects in working memory that are not directly
derived from outside data, or used as output. As their name implies, they're used to
explicitly control flow of the rules.
--- On Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz> wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the decision.
Usually that's an emergency case and it will be something like "this patient
needs to be admitted to hospital immediately". In other cases, we want to provide
some advice which a clinician may or may not choose to heed. It sounds to me that the
insertLogical mechanism might well work for those latter cases (was this what you were
referring to when you talked about 'control facts'?) In the other case - an
emergency when you need to give one element of critical advice then quit - is there an
option to terminate the rules immediately and return the current result?
Peter
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Swindells, Thomas
Sent: Wednesday, 9 March 2011 10:23 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
I don't think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time - if not control facts would
have to be the way to go.
You also need to make sure you actually tell the rule engine you have modified the patient
when you set their advice - you need to wrap the call with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On
Behalf Of Michael Anstis
Sent: 09 March 2011 07:58
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use of "null
advice", such that:-
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
insertLogical( new Diagnosis( $p ) );
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
not Diagnosis( patient == $p )
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
end
As David states, more specific rules should have higher salience than the more general
that should have lower. Salience controls conflict resolution, which is the order in which
activations on the agenda are evaluated, it does not control which rules are evaluated -
which happens as facts are inserted into working memory and not when fireAllRules( )
invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz
<http://mc/compose?to=petera@bestpractice.org.nz> >
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules independent of each
other to the maximal degree to which that is possible. That's why I didn' t want
to have isZombie==false in the general rule - I wanted the general case to be unaware of
the exceptions. The field in which I'm working is clinical decision support where
there might be a number of exceptions and corner cases. I'd like to be able to
express the core logic without reference to the corner cases and then deal with the
exceptions separately.
I think your idea of using salience but only adding advice if it hasn't already been
given fits the bill - that way the general case can be simple and not have to explicitly
exclude all the exception cases.
Thanks very much for the feedback - it's really valuable to get an idea about what
options are available and what's considered best practice.
Cheers!
Peter.
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of David
Faulkner
Sent: Wednesday, 9 March 2011 4:51 p.m.
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
"activation-group"; if two rules are in the same activation group, only one of
them will fire. Note that the rule with HIGHER salience will fire first; to accomplish
what you are looking for you'd have to give the exception rule a higher salience.
I would also note that although there are specific instances where activation-group has a
strong need, many in the community find that the most power and flexibility from the rule
engine comes from "letting go" of trying to exactly order your rule execution,
and instead letting the rule engine decide what would happen here. One way to accomplish
this in your case would be to simply add (isZombie == false) to your constraint on the
general rule. Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The possibilities
are endless.
With kind regards,
David Faulkner
david.faulkner(a)amentra.com <http://mc/compose?to=david.faulkner@amentra.com>
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of Peter
Ashford
Sent: Wednesday, March 09, 2011 7:24 AM
To: Rules Users List
Subject: Re: [rules-users] Misunderstanding salience?
Actually, I think I've figured this one out : in the Zombie case, it's firing both
rules and it's just that with the negative salience, the zombie exception rule is the
last rule fired, therefore, the last thing written into advice.
So... what would be the correct way to do what I'm trying to do here? The idea is
that the Zombie exception rule should fire in preference to the general rule and that none
of the general processing should occur at all (imaging that these rules had side-effects
for the rest of the system they're attached to, we don't want all the general rule
side effects to apply and then all the exception case side effects)
Thanks in advance!
Peter.
From: rules-users-bounces(a)lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org>
[mailto:rules-users-bounces@lists.jboss.org
<http://mc/compose?to=rules-users-bounces@lists.jboss.org> ] On Behalf Of Peter
Ashford
Sent: Wednesday, 9 March 2011 1:31 p.m.
To: rules-users(a)lists.jboss.org <http://mc/compose?to=rules-users@lists.jboss.org>
Subject: [rules-users] Misunderstanding salience?
Hi There
I'm new to drools. I've just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that's not working as I expect it
is the rule ordering via salience. This is my simple test rule set:
rule "General brain eating advice"
when
p : Patient(eatsBrains == true)
then
p.setAdvice("Stop eating brains, or at least, try to cut down");
end
rule "Zombie exception to brain eating advice"
salience -50
when
p : Patient(eatsBrains == true, isZombie == true)
then
p.setAdvice("Evidence suggests that the undead cannot contract Kuru or
that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
end
The idea is that the first rule fires all the time unless the patient happens to be a
zombie, in which case the exception rule (the second rule) kicks in. Now, as I have it
here, with the exception at salience at -50 it actually works, which is the opposite of
what I was expecting. I'd thought that I would have had to have the exception at a
higher salience to fire first. That was what I tried first but that didn't work -
everyone got the general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
"It is very difficult to get a man to understand something when his tribal identity
depends on his not understanding it" - Michael Bérubé on Republican climate change
denial.
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11:26 a.m.
I didn't actually read through all of the thread, but it sounds to me that
you're looking for "drools.halt()", which is something that you can
actually
call from the consequence part of your rules.
2011/3/9 Peter Ashford <petera(a)bestpractice.org.nz>
Ok, thanks. I can see how asserting a control fact would work here
– I
only asked about a terminate option to be able to avoid having to check for
the absence of the control fact in every rule, but that’s fine if that’s
what I have to do.
Thank s everyone for the help – it’s been excellent and very instructive
:o)
p.s.: No, I don’t use RuleFlow or jBPM. We’re writing DRL’s by hand and
it’s our expectation that we will have clinical content experts using Guvnor
to author rules once we’ve got our new system up and running. At this point
I’m just trying to establish what best practice for our domain ought to be.
Peter.
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Michael Anstis
*Sent:* Thursday, 10 March 2011 10:45 a.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
I don't suppose you (Peter) use RuleFlow or jBPM?
If not then remember rules' patterns are matched as facts are inserted into
WM. The resulting activations are ordered by controlling semantics such as
salience, no-loop, lock-on-active etc. Therefore should higher salience
rules activations (that will be executed first) alter the state of WM lower
salience rules' activations could be removed (by the presence of the control
fact or non-null "advice" depending on what approach you take) and hence not
be candidate for execution.
This is why, IMO, people talk about considering all rules executing in
parallel rather than sequentially.
If you're using jBPM then fail-fast is an option, but not something I know
much about.
Cheers,
Mike
2011/3/9 Greg Barton <greg_barton(a)yahoo.com>
"Control facts" is a term for objects in working memory that are not
directly derived from outside data, or used as output. As their name
implies, they're used to explicitly control flow of the rules.
--- On *Wed, 3/9/11, Peter Ashford <petera(a)bestpractice.org.nz>* wrote:
From: Peter Ashford <petera(a)bestpractice.org.nz>
Subject: Re: [rules-users] Misunderstanding salience?
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, March 9, 2011, 2:54 PM
Working with Zombies? No... although some of our clients....
A wrinkle we have is that sometimes an exception case should terminate the
decision. Usually that’s an emergency case and it will be something like
“this patient needs to be admitted to hospital immediately”. In other
cases, we want to provide some advice which a clinician may or may not
choose to heed. It sounds to me that the insertLogical mechanism might well
work for those latter cases (was this what you were referring to when you
talked about ‘control facts’?) In the other case – an emergency when you
need to give one element of critical advice then quit – is there an option
to terminate the rules immediately and return the current result?
Peter
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Swindells, Thomas
*Sent:* Wednesday, 9 March 2011 10:23 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
I don’t think you even need it that complicated.
Just have your constraints in the form
Patient(advice == null, ...)
This assumes you only give the patient one advice at a time – if not
control facts would have to be the way to go.
You also need to make sure you actually tell the rule engine you have
modified the patient when you set their advice – you need to wrap the call
with a modify(p) {...}.
Hope you get your zombies under control soon,
Thomas
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Michael Anstis
*Sent:* 09 March 2011 07:58
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
You had me fooled Peter, I thought you worked in a zombie related field ;-)
Control Facts can also be used, which I think David eluded to with his use
of "null advice", such that:-
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
insertLogical( new Diagnosis( $p ) );
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
not Diagnosis( patient == $p )
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
insertLogical( new Diagnosis( $p ) );
*end*
As David states, more specific rules should have higher salience than the
more general that should have lower. Salience controls conflict resolution,
which is the order in which activations on the agenda are evaluated, it does
not control which rules are evaluated - which happens as facts are inserted
into working memory and not when fireAllRules( ) invoked.
With kind regards,
Mike
2011/3/9 Peter Ashford
<petera@bestpractice.org.nz<http://mc/compose?to=petera@bestpractice.org.nz>
>
Thanks for the ideas, David.
What I ultimately want to achieve is to have the individual rules
independent of each other to the maximal degree to which that is possible.
That’s why I didn’ t want to have isZombie==false in the general rule – I
wanted the general case to be unaware of the exceptions. The field in which
I’m working is clinical decision support where there might be a number of
exceptions and corner cases. I’d like to be able to express the core logic
without reference to the corner cases and then deal with the exceptions
separately.
I think your idea of using salience but only adding advice if it hasn’t
already been given fits the bill – that way the general case can be simple
and not have to explicitly exclude all the exception cases.
Thanks very much for the feedback – it’s really valuable to get an idea
about what options are available and what’s considered best practice.
Cheers!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *David Faulkner
*Sent:* Wednesday, 9 March 2011 4:51 p.m.
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Peter,
The EXACT way to accomplish the functionality that you are looking for is
“activation-group”; if two rules are in the same activation group, only one
of them will fire. Note that the rule with HIGHER salience will fire first;
to accomplish what you are looking for you’d have to give the exception rule
a higher salience.
I would also note that although there are specific instances where
activation-group has a strong need, many in the community find that the most
power and flexibility from the rule engine comes from “letting go” of trying
to exactly order your rule execution, and instead letting the rule engine
decide what would happen here. One way to accomplish this in your case would
be to simply add (isZombie == false) to your constraint on the general rule.
Another way that involves salience but NOT agenda groups is to set a high
salience on your exception rule, but only add advice if advice is null. The
possibilities are endless.
With kind regards,
David Faulkner
david.faulkner@amentra.com<http://mc/compose?to=david.faulkner@amentra.com>
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, March 09, 2011 7:24 AM
*To:* Rules Users List
*Subject:* Re: [rules-users] Misunderstanding salience?
Actually, I think I’ve figured this one out : in the Zombie case, it’s
firing both rules and it’s just that with the negative salience, the zombie
exception rule is the last rule fired, therefore, the last thing written
into advice.
So... what would be the correct way to do what I’m trying to do here? The
idea is that the Zombie exception rule should fire in preference to the
general rule and that none of the general processing should occur at all
(imaging that these rules had side-effects for the rest of the system
they’re attached to, we don’t want all the general rule side effects to
apply and then all the exception case side effects)
Thanks in advance!
Peter.
*From:*
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>[mailto:
rules-users-bounces@lists.jboss.org<http://mc/compose?to=rules-users-bounces@lists.jboss.org>]
*On Behalf Of *Peter Ashford
*Sent:* Wednesday, 9 March 2011 1:31 p.m.
*To:*
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
*Subject:* [rules-users] Misunderstanding salience?
Hi There
I’m new to drools. I’ve just set up the Drools-Server and it is (finally!)
working and serving my test rule-set. The one thing that’s not working as I
expect it is the rule ordering via salience. This is my simple test rule
set:
*rule* "General brain eating advice"
*when*
p : Patient(eatsBrains == *true*)
*then*
p.setAdvice("Stop eating brains, or at least, try to cut
down");
*end*
*rule* "Zombie exception to brain eating advice"
*salience* -50
*when*
p : Patient(eatsBrains == *true*, isZombie == *true*)
*then*
p.setAdvice("Evidence suggests that the undead cannot
contract Kuru or that the effects are irellevant given the " +
"patient's current zombified state.\nSuggest
euthenasing patient lest he/she eat your (or someone " +
"else's) brains");
*end*
The idea is that the first rule fires all the time unless the patient
happens to be a zombie, in which case the exception rule (the second rule)
kicks in. Now, as I have it here, with the exception at salience at -50 it
actually works, which is the opposite of what I was expecting. I’d thought
that I would have had to have the exception at a higher salience to fire
first. That was what I tried first but that didn’t work – everyone got the
general advice, zombies included.
What am I misunderstanding here?
Thanks!
Peter.
---
“It is very difficult to get a man to understand something when his tribal
identity depends on his not understanding it” - Michael Bérubé on
Republican climate change denial.
_______________________________________________
rules-users mailing list
rules-users@lists.jboss.org<http://mc/compose?to=rules-users@lists.jboss.org>
https://lists.jboss.org/mailman/listinfo/rules-users
------------------------------
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have received this message in error, please immediately notify the
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The content of e-mails as well as traffic data may be monitored by NDS for
employment and security purposes. To protect the environment please do not
print this e-mail unless necessary.
NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18
4EX, United Kingdom. A company registered in England and Wales. Registered
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5067
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5069
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12 comments
7 participants
participants (7)
-
David Faulkner -
Greg Barton -
Leonardo Gomes -
Michael Anstis -
Peter Ashford -
Swindells, Thomas -
Wolfgang Laun