[rules-users] Rules writing best practice?

[Greg Barton]

Anything gathered using the "from" keyword will not use the rete algorithm to determine whether refetching is appropriate or not. (i.e. no awareness of whether the fetched data is constant for a given fact.)  Whenever a "from" condition is encountered the fetch is performed, so use it with care if efficiency is a concern.

--- On Tue, 2/9/10, Brice Figureau <brice+drools at daysofwonder.com> wrote:

> From: Brice Figureau <brice+drools at daysofwonder.com>
> Subject: [rules-users] Rules writing best practice?
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Date: Tuesday, February 9, 2010, 3:40 AM
> Hi,
> 
> Is there a rules writing best practice document somewhere?
> 
> I'm asking the question because as a newbie rule writer
> (which doesn't
> know anything about the underlying drools matching
> algorithm), I'm
> wondering if my rules will behave gracefully.
> 
> For instance, I (ab)use a lot the from/accumulate to bring
> in the
> knowledge some external facts coming from some DAO. 
> All my rules use one time or more the same "from
> dao.getInformationFromDatabase( <inserted fact> )"
> structure and I'm not
> sure the algorithm is smart enough to cache this
> information which is
> constant for a given inserted fact.
> 
> Should I instead insert all this information as facts prior
> to the rules
> firing?
> -- 
> Brice Figureau
> My Blog: http://www.masterzen.fr/
> 
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