Sure, I agree, this would be an example:-<br><br><span style="font-family: courier new,monospace;">rule "Family smurf"</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">when</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> MyFact( smurf == "pupa" )</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> ExternalObject( ) from placeHolder.namedQuery("Smurfs")</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">then</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> //Do something</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">end</span><br><br>If <span style="font-family: courier new,monospace;">MyFact</span> is updated in other rules the list will be refreshed "from" the named query.<br>
<br>So the preference might be to load the Objects into WM first:-<br><br><span style="font-family: courier new,monospace;">rule "bootstrap"</span><br><span style="font-family: courier new,monospace;">salience -100</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">when</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> $list : List( ) from placeHolder.namedQuery("Smurfs")</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">
then</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> for(ExternalObject o : $list ) {</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> insert( o );</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> }</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">end</span><br style="font-family: courier new,monospace;"><br>
<span style="font-family: courier new,monospace;">rule "Family smurf"</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">when</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;"> MyFact( smurf == "pupa" )</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> ExtenalObject( )</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">then</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;"> //Do something</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">end</span><br><br>
You could also have a layer of caching between the rules and RDBMS too; so your only performing a read from cache with the "from" keyword and not RDBMS itself.<br><br>How you choose is obviously up to you and the volatility of your data read from RDBMS.<br>
<br><br><br><div class="gmail_quote">2011/2/14 Mauricio Salatino <span dir="ltr"><<a href="mailto:salaboy@gmail.com">salaboy@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Beware with the use of the FROM Conditional Element, because if you are using another fact that doesn't come from the DB and you change them, the FROM CE will be continuously evaluated causing the execution of tons of queries multiple times.<br>
My two cents.<br>Greetings<br><br><div class="gmail_quote">2011/2/14 Michael Anstis <span dir="ltr"><<a href="mailto:michael.anstis@gmail.com" target="_blank">michael.anstis@gmail.com</a>></span><div><div></div><div class="h5">
<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
You can access Objects from external resources using the "from" keyword (in fact the use of this with Hibernate named queries is a documented use-case, IIRC).<br><br>The Objects are not however inserted into WorkingMemory using "from" are should therefore be time-constant as their properties will not be included in truth maintenance.<br>
<br>If you require the Objects as Facts in WorkingMemory for the inference engine to reason with, you can write rules using "from" that insert into WorkingMemory.<div><div></div><div><br><br><div class="gmail_quote">
On 14 February 2011 11:27, hyjshanghai <span dir="ltr"><<a href="mailto:hyjshanghai@gmail.com" target="_blank">hyjshanghai@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
As far as I know, Drools can only reason over facts in the working memory. It<br>
can not directly "select" from RDBMS. You have to load in all data items<br>
from the database and validate them in memory by Drools.<br>
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View this message in context: <a href="http://drools-java-rules-engine.46999.n3.nabble.com/Applying-rules-on-the-data-in-an-RDBMS-tp2468317p2491888.html" target="_blank">http://drools-java-rules-engine.46999.n3.nabble.com/Applying-rules-on-the-data-in-an-RDBMS-tp2468317p2491888.html</a><br>
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<br></blockquote></div></div></div><font color="#888888"><br><br clear="all"><br>-- <br> - CTO @ <a href="http://www.plugtree.com" target="_blank">http://www.plugtree.com</a> <br> - MyJourney @ <a href="http://salaboy.wordpress.com" target="_blank">http://salaboy.wordpress.com</a><br>
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