[rules-users] Working with dates in rules

[Anstis, Michael (M.)]

Hi David,
 
Sorry it was of little help.
 
A rule of thumb is to stay away from "eval" as it kills performance (the
patterns can't be indexed).
 
I'm not sure if Drools can handle Date variables (the docs state it
handles Data literals formatted as "dd-mmm-yyyy" so Cheese( date ==
"27-Oct-2008") works).
 
I guess you could look at something like this (gees, this is going to
show how "green" I am with Drools now):-
 
rule "yuck"
    when
        DateFactory($today : today )
        $c : CreditCard( $expires : expirationDate )
        ArrayList( size >= 0 ) from collect( Day( date >= $today, date
<= $expires ))
    then
        //Difference between "today" and "expiry date" is more than zero
days
end
 
This does require the insertion of (possibly) huge amounts of Day facts.
Yuck. There must be a better way (in fact your eval looks soooo much
cleaner). I'm just throwing out ideas. 
 
Good luck with your adventures with Drools.
 
Mike


________________________________

	From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of David Siefert
	Sent: 29 January 2009 11:31
	To: Rules Users List
	Subject: Re: [rules-users] Working with dates in rules
	
	
	Not sure--Drools 5 temporal reasoning looks like it would be the
answer.  Only problem is that I need a solution now, so I am stuck with
Drools 4.
	 
	This did give me some ideas though.  I created myself a class
called TemporalReasoner.  This has a few methods, namely to roll a date
(so I can tell it x amount of time from now), and then compare it to
another date.
	 
	So in my rule, lets say I have a fact CreditCard with property
expiration:Date (speaking uml-ishly for "a property named 'expiration'
of type Date"):
	 
	rule "Fires when expiration less than today"
	  when
	    $c: CreditCard($expires : expirationDate)
	    eval(new
TemporalReasoner(Calendar.getInstance()).lessThan($expires))
	  then
	    // do something for when credit card is still valid
	end
	 
	Now, I'm still generally a noob with BRs, so I'm not sure how
this will affect performance.  Any advice?
	 
	Thanks,
	David
	
	
	On Thu, Jan 29, 2009 at 3:50 AM, Anstis, Michael (M.)
<manstis1 at ford.com> wrote:
	

		Hi,
		 
		I wonder whether Drools 5 "Complex Event Processing
Support (Temporal Reasoning)" might be what you're looking for?
		 
	
http://blog.athico.com/2008/07/drools-50-m1-new-and-noteworthy.html
		 
		With kind regards,
		 
		Mike


________________________________

			From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of David Siefert
			Sent: 29 January 2009 09:40
			To: Rules Users List
			Subject: [rules-users] Working with dates in
rules
			
			
			Hi-
			 
			I'm wondering how it would be possible to
compare a part of a date in the lhs condition of a rule in a Drool.  In
other words, I need to compare a date to see if it is x days from the
current date, n hours from current time, etc.  Would anyone be kind
enough to provide an example?  I'm thinking I may have to implement
something of my own to offer that functionality?
			 
			Big thanks,
			David


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