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.

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.

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:

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.