<font size=2 face="sans-serif">so you are using drools to build on-the-fly
queries based on user input. You could probably do this via "static"
rules. Since you basically have 4 variables (</font><tt><font size=2>price,
avg_user_rating, num_ratings, category), you could write 4 rules, one each
that filters based on one of the 4 variables and then chain the execution
through salience:</font></tt>
<br>
<br><tt><font size=2>rule price:</font></tt>
<br><tt><font size=2>salience 1</font></tt>
<br><tt><font size=2>when </font></tt>
<br><tt><font size=2> $p: Product(price
in param)</font></tt>
<br><tt><font size=2>then</font></tt>
<br><tt><font size=2> add $p to result</font></tt>
<br>
<br><tt><font size=2>rule avg_user_rating:</font></tt>
<br><tt><font size=2>salience 2</font></tt>
<br><tt><font size=2>when</font></tt>
<br><tt><font size=2> $p: Product(avg_user_rating
> param)</font></tt>
<br><tt><font size=2>then</font></tt>
<br><tt><font size=2> add $p to result</font></tt>
<br>
<br>
<br><tt><font size=2>and so on</font></tt>
<br>
<br>
<br>
<br>
<br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">soumya_sd <soumya_sd@yahoo.com></font>
<br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif">rules-users@lists.jboss.org,
</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">05/09/2012 08:43 AM</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">Re: [rules-users]
Is there a faster way of doing this in Drools ?</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Sent by:
</font><font size=1 face="sans-serif">rules-users-bounces@lists.jboss.org</font>
<br>
<hr noshade>
<br>
<br>
<br><tt><font size=2><br>
Vincent Legendre wrote<br>
> <br>
> Users changing rules IS the correct use-case of drools (I would even
say<br>
> that if rules never change, drools is likely to be worse than pure
java).<br>
> What others said is "changing the rules at each request by regenerating<br>
> and recompiling" is not.<br>
> <br>
> I can't imagine that users may change rules at each request, so you
must<br>
> have, at least for some time (thus a lot of requests), a stable rule
base.<br>
> What is costly is to compile rules, but you already know that.<br>
> So the idea is to keep in some kind of cache the actual rules, and
only<br>
> recompile them when they change.<br>
> <br>
> The source of rules does not matter : you can generate the DRL according<br>
> to your configuration, or make you users directly write rules (with<br>
> guvnor, which will fits well if your rules are only basic filters).<br>
> <br>
> The optimisation you have to do is to keep your compiled rules somewhere<br>
> (by serializing your KnowlegdePackages or simply keep it in a kind
of<br>
> map), and reuse it until your source change : you have to find a way
to<br>
> detect that rules (or the config that is used to generate them) have<br>
> changed, and then recompile a new up-to-date KnowledgePackage.<br>
> <br>
> <br>
<br>
Thank you for your insights. <br>
<br>
At this point I'm designing for the worst case i.e., I'm assuming the rules<br>
with change with every request. <br>
<br>
Moreover, this can happen on a regular basis in the system I'm trying to<br>
design. <br>
<br>
Product<br>
{ <br>
price<br>
ave_user_rating<br>
num_ratings<br>
category <br>
<br>
} <br>
<br>
User wants to see Product with with the following rules <br>
<br>
at t=t_1 : If product.category in {A,B}. <br>
<br>
at t=t_2 : If product.category in {A,B} AND price < 100 <br>
<br>
at t=t_3 : If product.category in {A,B} AND price < 100
AND num_ratings ><br>
100 <br>
<br>
You can imagine the user changing these rules in a span of less than a<br>
minute. <br>
<br>
I understand that Drools is designed for cases when rules changes often.
But<br>
can it support something like the one I described above where rules are<br>
changing at a much faster rate? <br>
<br>
<br>
Thanks. <br>
<br>
<br>
<br>
<br>
<br>
<br>
--<br>
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