[rules-users] Grouping and Aggregation in Drools

[Manav]

Hi, 
I have a slightly tricky problem on my hand that i am trying to solve using 
rules. 

I am using version 5.1 of Drools.Appreciate if there are any suggestions / 
pointers . 


I have a customer who will have a shopping cart with various products. For 
example 

the shopping cart will be a list of products that belong to a certain 
sub-category and 

super category like 

product-id= 'Noodles', sub-category='PackagedFood', super-category='FMCG-Food', 
%value of total=3%
product-id= 'Cookies', sub-category='PackagedFood',super-category='FMCG-Food', 
%value of total=6%
product-id= 'Pizza', sub-category='ReadyToEat',super-category='FMCG-Food', 
%value of total=5%
product-id= 'Burgers', sub-category='ReadyToEat',super-category='FMCG-Food', 
%value of total=7%
product-id= 'Shampoo', sub-category='Toiletaries',super-category='FMCG-NonFood', 
%value of total=4%
product-id= 'Conditioner', 
sub-category='Toiletaries',super-category='FMCG-NonFood', %value of total=8%

The customer will also have a suggested cart that serves as a reference at the 
sub-category and supercategory level. The reference will tell what level of his 
total purchase he can spend on the sub-category and super-category. The 
reference will look something like 


super-category='FMCG-Food', %value-suggested=20%
super-category='FMCG-NonFood', %value-suggested=15%
sub-category='PackagedFood',%value-suggested=10%
sub-category='ReadyToEat',%value-suggested=10%
sub-category='Toiletaries',%value-suggested=6%

Looking at this example the customer is going overboard in the FMCG-Food super 
category as the suggested 

limit is 20% and the actual grouped at the supsercategory is 21% . Also he is 
crossing the limit at the 

sub-category level for ReadyToEat (suggested is 10% vs actual is 12%) and 
Toiletaries (suggested is 6% vs actual 12%)

My problem is how do i  group the actual data at various supercategory level, 
sum the %value and then compare it with the suggested in the when clause. 


If they cross the limit i will then have some action taken in the then clause. 
Similarly i will have to do the same at the sub-category level as well. 
Regards,
Manav