[rules-users] Struggling with Rule syntax - please help...

[Edson Tirelli]

   James,

   What are the "elements" in your list? Strings?

   There are a few ways of doing it. Basically they differ on what are 
the elements of your list, how many you expect to find in each list, 
etc. The simplest way:

when
    $code : String() from lookupDAO.getLookup(...)
    ( SHIPMENT_MOVE(customer_code == "abc", ship_code == $code ) OR
      SHIPMENT_MOVE(customer_code == "abc", deliver_code == $code ) OR
      SHIPMENT_MOVE(customer_code == "abc", port_code == $code )
    )
then
   // consequence
end

   Remember that if your list contains codes that match more than one 
condition above, your consequence will fire multiple times.
   If you want it to fire only once, you can use a predicate:

when
    $code : String() from lookupDAO.getLookup(...)
    SHIPMENT_MOVE(customer_code == "abc", $sc : ship_code,
                                      $dc : deliver_code, $pc : port_code,
                                      ( $code.equals($sc) || 
$code.equals($dc) || $code.equals($pc) ) )
    )
then
   // consequence
end

   If you expect your list to have a lot of objects, or if you expect to 
use the same list in more than one rule, you can improve performance by 
doing a rule to retrieve and assert the list of codes, based on whatever 
criteria you need (customer code for instance in the bellow example):

rule "retrieving the list"
when  
    Customer( $custCode : customer_code )
then
    List codes = lookupDAO.getLookup( $custCode );
    assert( codes );
end

rule "doing something"
when
    Customer( $custCode : customer_code )
    $list : List()
    SHIPMENT_MOVE(customer_code == $custCode, $sc : ship_code,
                                      $dc : deliver_code, $pc : port_code,
                                      ( $list.containts($sc) || 
$list.containts($dc) || $list.containts($pc) ) )
then
    // do something
end

   If your DAO returns a specific class, like the one mentioned in one 
of your examples bellow (LookupTableResults) and it is not a collections 
implementation, you can even do things like:

 when
    SHIPMENT_MOVE(customer_code == "abc", $sc : ship_code,
                                      $dc : deliver_code, $pc : port_code )
    LookupTableResult( elements contains $sc | contains $dc | contains 
$pc ) from lookupDAO.getLookup(...)
    )
then
   // consequence
end

   So, I don't have your code to run, but there are many ways of 
doing... test and try to find which one best suites you.

   Hope it helps.

    Edson
 

jdepaul wrote:

>I'm having trouble figuring out syntax for my rules - could someone please
>steer me in the right direction - it's been a frustrating few days and no
>luck.  I need to check existence of various attributes from the
>SHIPMENT_MOVE fact against a list of values (same list) I fetch from the
>DB...
>
>
>Get $valuesList from a DAO - then...
>
>If SHIPMENT_MOVE.customer_code = "abc" and SHIPMENT_MOVE.reference_code
>exists in $valuesList
>OR 
>SHIPMENT_MOVE.customer_code = "abc" and SHIPMENT_MOVE.shipping_code exists
>in $valuesList
>OR
>SHIPMENT_MOVE.customer_code = "abc" and SHIPMENT_MOVE.partner_code exists in
>$valuesList
>
>
>
>I have the following rule working fine:
>
>$shipment SHIPMENT_MOVE(customer_code = "abc")
>	LookupTableResult ( resultValue == 1 ) from lookupDAO.getLookup(...)
>	
>But I'm having real problems with writing a rule like this:
>
>when
>	SHIPMENT_MOVE(customer_code == "abc", $list contains ship_code) OR
>	SHIPMENT_MOVE(customer_code == "abc", $list contains deliver_code) OR
>	SHIPMENT_MOVE(customer_code == "abc", $list contains port_code)
>	
>Your guidance will be appreciated - 
>
>Thanks,
>James
>
>P.S. 
>I'm using Drools 3.1.0M1
>  
>


-- 
 Edson Tirelli
 Software Engineer - JBoss Rules Core Developer
 Office: +55 11 3124-6000
 Mobile: +55 11 9218-4151
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