[rules-users] How to get correct version of rules based on effective date

[Faisal Shafique]

Thats a good question I should have been more clear. Better example would be something like Federal Tax. Lets say there was a tax deduction allowed for buying a hybrid car in 2008. In 2009, due to changes in tax policy, this deduction is not allowed anymore. In 2010, policy again changed to allow this deduction but only for half the cost of the car. Now lets say that a person is filing for tax year 2008, 2009 and 2010 together. Effective date for running the tax rules would be 2008, 2009 and 2010 in this case. User will enter these dates on screen one by one, running the rules each time and calculate their taxes. System should be able to use correct rules which were effective at the time as per the effective date that user enters.
To answer your question, rules themselves change and not just parameters. We already have a db based infrastructure for pulling out correct parameters (e.g tax bracket limits) based on effective date. 
As its a huge eligibility system, rules changes because of policy are common and this is a very common use case for government eligibility systems. We need a way to implement this which is performant, scalable (e.g should not slow down over time because of different rules versions) and easily maintanable. 
Somebody mentioned about pulling correct version from repository. That IMHO is more like version control system and very coarse grained. We need to be able to version rule by rule or may be resource like drl files.
Thanks for your help.


On Feb 21, 2011, at 2:13 AM, "Swindells, Thomas" <TSwindells at nds.com> wrote:

> Do your rules actually change over time or just the paramaters in your rules change?
> 
> If the later then you could structure your rules so they don’t have values hard coded but instead depend upon an Object (InterestRate) to provide them and you code just loads the appropriate InterestRate object when the query starts.
> 
>  
> 
> Thomas
> 
>  
> 
> From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Wolfgang Laun
> Sent: 21 February 2011 09:08
> To: Rules Users List
> Subject: Re: [rules-users] How to get correct version of rules based on effective date
> 
>  
> 
> There may be one rule to determine the interest rates depending on date and whatever, and then there should be rules to do the calculation for some type of deposit (savings, loand,...) with the previously established rate.
> 
> Do not replicate calculation rules for various date intervals.
> 
> -W
> 
> 
> On 21 February 2011 05:36, Faisal Shafique <just_faisal at yahoo.com> wrote:
> 
> Hi,
> 
> We are evaluating Drools to replace a big legacy eligibility system in government sector. One of the critical requirement is to have the system pull correct rule based on a date e.g interest rate was 5% till 12/31/2010 but changed to 6% from 1/1/2011. If we are running rules in 2010 or before, calculation should use 5% else it should use 6%. Rules will run with a user clicking a button and results will be shown to user so probably a StatelessSession will be used. Something like AgendaFilters to filter rules based on a date probably will not be very scalable since over time we'll have lot of different temporal version of rules and all of them will have to be in KnowledgeBase for AgendaFilter to work which will be memory intensive and un-needed.IMHO, we should build KnowledgeBase with correct version of rules in the first place. Any ideas or pointers?
> 
> Thanks
> 
> 
> 
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