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<TITLE>RE: Using Drools as a glorified Hashmap</TITLE>
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<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">How many match rules do you have? You could always set a single</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Consolas">“</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">invalid</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">”</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas"> rule with a low sa</FONT><FONT FACE="Consolas">lience (at least lower than your match rules) that is always true and sets the flag</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas"> that it is invalid. Then put all the rules into the same activation-group so that only one can fire. If the invalid flag is set, that means that the</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Consolas">‘</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">no match</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">’</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas"> rule was</FONT><FONT FACE="Consolas"> the only one that could have fired. If it matches, the activation-group will prevent the</FONT></SPAN><SPAN LANG="en-us"> <FONT FACE="Consolas">‘</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">no match</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">’</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas"> rule from firing</FONT></SPAN><SPAN LANG="en-us"><FONT FACE="Consolas">…</FONT></SPAN><SPAN LANG="en-us">.</SPAN></P>
<P DIR=LTR><SPAN LANG="en-us">------------------------------</SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Message: 3</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Date: Tue, 18 May 2010 02:56:21 -0700 (PDT)</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">From: djb <dbrow</FONT><FONT FACE="Consolas">nell83@hotmail.com></FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Subject: [rules-users] Using Drools as a glorified Hashmap</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">To: rules-users@lists.jboss.org</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Message-ID: <1274176581461-825851.post@n3.nabble.com></FONT></SPAN></P>
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<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Hi Drools users,</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">I've got a situation where I've got a list of Drug codes which can only be</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">used for certain prescription codes.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">The traditional method for implementing this is to simply pre-load the</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">values in a static Hashmap. Then if get() returns null, it is not a val</FONT><FONT FACE="Consolas">id</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">combination. O(1), blazingly fast. </FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">The issue with using Drools for this, is that Drools can match a code to a</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">code, and mark it as valid, but cannot call it invalid, as another rule may</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">still be relevant. Therefore, using Drools for this would requi</FONT><FONT FACE="Consolas">re marking</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">combinations as valid, and afterwards, doing a linear traversal of the</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">prescriptions to see if there are any combinations that are not valid.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Is this the case? I would like to try implement it in Drools just for the</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">sake of consistency, but it</FONT><FONT FACE="Consolas"> seems a bit of a hack.</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Thanks,</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Daniel</FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">-- </FONT></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">View this message in context:</FONT></SPAN><SPAN LANG="en-us"> </SPAN><A HREF="http://drools-java-rules-engine.46999.n3.nabble.com/Using-Drools-as-a-glorified-Hashmap-tp825851p825851.html"><SPAN LANG="en-us"><U><FONT COLOR="#0000FF" FACE="Consolas">http://drools-java-rules-engine.46999.n3.nabble.com/Using-Drools-as-a-glorified-Hashmap-tp825851p825851.html</FONT></U></SPAN><SPAN LANG="en-us"></SPAN></A><SPAN LANG="en-us"></SPAN></P>
<P DIR=LTR><SPAN LANG="en-us"><FONT FACE="Consolas">Sent from the Drools - User mailing list archive at Nabble.com.</FONT></SPAN></P>
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