Hi Mike,
Thanks very much, after a few minutes of staring I think I have understood
your very well put answer!
If I understand you right, what is happening is:
Test( $y : y )
This means, WHEN there is an instance of Test, assign the value of its "y"
property to $y
AND
WHEN there is an instance of Test where it's "x" property is equal to $y +
1
THEN fire.
I think I understand that. I am going to need to do this with some pretty
complicated formulae, containing up to 8 different variables. I have a fixed
data set and need to find certain patterns in them based on the formulae. I
have most of the program figured out, my only trouble is expressing my
formulae in the correct syntax. I will try to extend this principle you have
explained to me and hope it can cope with the extra complication... unless
there would be a better way to achieve this?
I am really sorry but I am totally new to drools - but am committed to using
it on a project so I guess I'm going to get to know it pretty well :-)
I read briefly that one can define a DSL, I might look at this eventually to
build an easier mechanism for expressing my formulae - if that can be
achieved using a DSL.
Can the whole rule be defined in Groovy/Java - if so I might be easier doing
that. I have so much work to do!
many thanks
Richard
2008/5/2 Anstis, Michael (M.) <manstis1(a)ford.com>:
Hi Richard,
The "when" section matches fact (object) patterns, so your requirement
could be written as:-
when there is a Test Fact 'A' and another Test Fact 'B' where "the
'x'
property of 'A'" equals "the 'y' property of fact 'B'
plus 1" then.....
This would become:-
rule "Rule 1"
when
Test( $y : y )
Test( x == ($y + 1) )
then
System.out.println("Rule 1 matches");
end
By default both patterns can match the same object, so test data:-
A : x = 1, y = 1
B : x = 2, y = 1
Will cause the rule to activate twice:-
A and B
B and B
With kind regards,
Mike
------------------------------
*From:* rules-users-bounces(a)lists.jboss.org [mailto:
rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Richard Bremner
*Sent:* 02 May 2008 08:53
*To:* rules-users(a)lists.jboss.org
*Subject:* [rules-users] newbie question on "when" condition syntax
Hi,
say I have a class with two fields, x and y:
public class Test {
int x = 1;
int y = 2;
getters/setters...
}
I would like a rule which fires when y = x + 1
my initial thought would be something like:
rule "Rule 1"
when
test : Test (y == x + 1)
then
System.out.println("Rule 1 matches.");
end
but this is invalid syntax and I can not find any examples of such a rule.
I'm doing my best but reading the manual etc. I'm struggling with the syntax
here and can't figure it out.
any help really appreciated!
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