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Subject: RE: [rules-users] Drools basic questions.
Date: Thu, 17 May 2007 09:13:04 +0100
Message-ID: <6CE83AFC8500B641AE00AC1674A3B4AC0164BDFB@eu1wam08.warley.ford.com>
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Thread-Topic: [rules-users] Drools basic questions.
Thread-Index: AceYUy01C62SgTUeR6SRPDF1zBXw0AABxpcg
From: "Anstis, Michael \(M.\)" <manstis1@ford.com>
To: "Rules Users List" <rules-users@lists.jboss.org>

Hi,

1. The dollar sign has no significance. What appears to the left of the
colon is simply an identifier binding the object\field to a variable.
Some people prefix their identifiers with dollar signs so that
identifiers are easier to see in code.

	$stilton : Cheese( type =3D=3D "stilton" )
      Cheesery( cheeses contains $stilton )

	stilton : Cheese( type =3D=3D "stilton" )
      Cheesery( cheeses contains stilton )

	some_identifier : Cheese( type =3D=3D "stilton" )
      Cheesery( cheeses contains some_identifier )

2.=20
    - cheapStilton : Cheese( type =3D=3D "stilton", price < 10 )
	Binds a variable "cheapStilton" to a Fact (Object) of type
Cheese where it's field "type" equals "stilton"=20
	and it's field "price" is less than 10. Both "type" and "price"
are compared to literals.

    - cheapStilton : Cheese( type =3D=3D "stilton", price < newPrice)
	Binds a variable "cheapStilton" to a Fact (Object) of type
Cheese where it's field "type" equals "stilton"
	and it's field "price" is less than another identifier
"newPrice". "Type" is compared to a literal and "price" is
	compared to a variable. The variable would need to have been
bound somewhere else in the rule; for example:-

	Price( newPrice : price )
    	cheapStilton : Cheese( type =3D=3D "stilton", price < newPrice)

With kind regards,

Mike

-----Original Message-----
From: rules-users-bounces@lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Mithun
Sent: 17 May 2007 06:04
To: rules-users@lists.jboss.org
Subject: [rules-users] Drools basic questions.


I am new to drools, so i have some basic doubts.=20

1. what does the dollar sign represent in the following rule? what is
the
difference when u prefix and dont prefix a variable with the dollar
sign?
    - $stilton : Cheese( type =3D=3D "stilton" )
      Cheesery( cheeses contains $stilton )

2. what is the difference between the following rule statements ?
    - cheapStilton : Cheese( type =3D=3D "stilton", price < 10 ) and
    - cheapStilton : Cheese( type =3D=3D "stilton", price < newPrice)

   how does the rule base get access to the variable newPrice, in the
above
rule statement? Please help.

Thank you.
--=20
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