[rules-users] Intermediate conclusions using strings

[David Cracauer]

We've encountered a similar situation where there were many paths to  
the same conclusion, and we needed to track them.  We found the best way
was to create a new Object that is created in the lhs and inserted.

The below pseudo code  should illustrate what I'm talking about.  
Hopefully it makes sense:

public class MembershipLevel{
	
	private Person person;
	private Date memberSince;
	private Level level;
	private Number revenue;	

	public MembershipLevel(Person person, Date memberSince, Level level,  
Number revenue){
				...
	}

	//getters and setters

	//appropriate equals/hashCode

}

rule "gold member if revenue per month > 1000"
  when ...
  then
	insert( new MemberShipLevel(person, Level.GOLD, revenue);
end

rule "gold member since 1999 gets a t-shirt"
when
	m:MemberShipLevel(  memberSince < '2000-01-01');
then
	TShirtFactory.sendShirtTo(m.getPerson());
end




This allows you to have more than one person in the engine at once,  
and you can track what caused the calculations.



On Aug 25, 2008, at 6:09 AM, David Boaz wrote:

>
> Hi all,
>
> I have an idea and I want to get the community feedback.
>
> Many times there are many ways to reach an intermediate conclusion.  
> This
> conclusion can be used to derive higher level conclusions or actions.
> For example, assuming a credit application has several (or) options to
> conclude whether a parson is classified as gold member. Then, other  
> rules
> need this information to determine the credit limit for that member.  
> To
> note, the Person java class doesn't have a specialized attribute for  
> the
> classification. The classification is only an internal means to  
> simplify the
> application logic.
> To solve that problem, I thought to insert a string conclusion to  
> the WM.
> Something like:
>
> rule "gold member if revenue per month > 1000"
>  when ...
>  then insert("gold member")
> end
>
> rule "gold member if total amount > 1000000"
>  when ...
>  then insert("gold member")
> end
> ...
> rule r100
>  when String(value=="gold member")
>  then...
> end
>
> * Is it an appropriate approach?
> * I know it ugly to use the same string literal in various rules.  
> Can we
> avoid that?
> * Is there a known mechanism to handle these cases?
>
> Thanks, David
> -- 
> View this message in context: http://www.nabble.com/Intermediate-conclusions-using-strings-tp19141834p19141834.html
> Sent from the drools - user mailing list archive at Nabble.com.
>
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