What you have described is half of the usage of binding variables. You can bind a variable to a fact or to individual fields of a fact. You can then use those variables in the LHS or the RHS of your rules. For example: 1.- Find different Person objects when $p1: Person($name1: name) $p2: Person($name2: name, *this != $p1*) then System.out.println("Found "+$p1+" with name '"+$name1+"' and "+$p2+" with name '"+$name2+"'"); end Regards, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Esteban Aliverti - Blog @ http://ilesteban.wordpress.com On Thu, May 9, 2013 at 3:08 PM, IPatel <ishita.patel(a)usbank.com&gt; wrote:

Hi, Can you please elaborate your query about :=? Thanks, Abhinay -- View this message in context: http://drools.46999.n3.nabble.com/Use-of-the-binding-variable-tp4023744p4... Sent from the Drools: User forum mailing list archive at Nabble.com.

The unification operator ":=" is a combination of the binding operator ":" and the equality operator "==". In fact, it behaves as either, depending on the context: In this example, we are looking for two different Persons with the same name: rule "Pairs" when $p := Person( $name := name ) Person( this != $p, $name := name ) then System.out.println( "We have two persons with the same name : " + $name ); end The LHS is equivalent to: $p : Person( $name : name ) Person( this != $p, name == $name ) The first time a variable such as $name is used with ":=", it works as ":". Any time later, since the variable now has a value assigned to it, ":=" will work as "==". Apparently, this operator may seem redundant and useless :) but it is actually meant to be used with **queries**. For example: query personsByName( String $name, Person $p ) $p := Person( $name := name ) end The arguments ($name, $p) can be BOTH IN and OUT parameters, depending on the context of the caller. So, the query can be used in 4 different ways: IN/IN : Is this Person in the WM and does it have this name? ?personsByName( "john", p1 ) IN/OUT : Retrieve all Persons with this name ?personsByName( "john", $pers ) OUT/IN : Retrieve this person, if it is in the WM, and return its name ?personsByName( $n, p1 ) OUT/OUT : Retrieve all persons from the WM with their names ?personsByName( $n, $pers ) Fir this reason, it is impossible for the query to know whether, upon invocation, $name and $p will be IN - and thus already have a value - or OUT. So, the unification operator ":=" is necessary because of its polymorphic ability to behave as ":" or "==" as appropriate. Best Davide On 05/09/2013 06:51 AM, Sonata wrote:

Hi, Our business partners will be using Guvnor to write the business rules so i am also not sure what is ":=?". If you can explain that will be good. Thank you Isha -- View this message in context: http://drools.46999.n3.nabble.com/Use-of-the-binding-variable-tp4023744p4... Sent from the Drools: User forum mailing list archive at Nabble.com.

Hi, I am still trying to convinece them to use the tool. I was under the impression that this tool is open source and no need to pay any license cost. It is interesting to find out that there is a cost associated with it. Does anyone know what other costs are associated with using this tool?? Thank you Isha -- View this message in context: http://drools.46999.n3.nabble.com/Use-of-the-binding-variable-tp4023744p4... Sent from the Drools: User forum mailing list archive at Nabble.com.

And yes, thank you Michael for clarifying the licensing fee question. Not sure why my company said that. May be it is different when it comes to business -- View this message in context: http://drools.46999.n3.nabble.com/Use-of-the-binding-variable-tp4023744p4... Sent from the Drools: User forum mailing list archive at Nabble.com.