[rules-users] order of injected events

[Chris Richmond]

Wolfgang,

Thanks very much for that explanation, it cleared up many questions.

"...If the order of your concurrently arriving events is essential, you 
may have to insert an ordinal as a property..."

Can you expand on this idea or in an general practice for handling real 
time streams of data that need to be processed in order they were injected?

Thanks,
Chris




On 7/21/2011 7:54 PM, Wolfgang Laun wrote:
> The insertion of DataReading events happens "instantaneously", without 
> Drools regaining "consciousness" in between. So, when the Engine wakes 
> up, it finds 20 activations in its agenda, with the same salience. Tie 
> breaking is defined to use LIFO.
>
> Running the Engine in real time, these 20 events are indeed 
> concurrently from the Engine's point of view, and any order of firings 
> is justified; all the more so because your rule contains nothing to 
> prefer a firing of an older event.
>
> If the order of your concurrently arriving events is essential, you 
> may have to insert an ordinal as a property.
>
> Cheers
> -W
>
> On 22 July 2011 11:07, Chris Richmond <crichmond at referentia.com 
> <mailto:crichmond at referentia.com>> wrote:
>
>     I am running a simple test like so:
>
>     package com.sample;
>
>     import org.drools.KnowledgeBase;
>     import org.drools.KnowledgeBaseFactory;
>     import org.drools.builder.KnowledgeBuilder;
>     import org.drools.builder.KnowledgeBuilderError;
>     import org.drools.builder.KnowledgeBuilderErrors;
>     import org.drools.builder.KnowledgeBuilderFactory;
>     import org.drools.builder.ResourceType;
>     import org.drools.io.ResourceFactory;
>     import org.drools.logger.KnowledgeRuntimeLogger;
>     import org.drools.logger.KnowledgeRuntimeLoggerFactory;
>     import org.drools.runtime.KnowledgeSessionConfiguration;
>     import org.drools.runtime.StatefulKnowledgeSession;
>     import org.drools.runtime.conf.ClockTypeOption;
>     import org.drools.runtime.rule.WorkingMemoryEntryPoint;
>
>     import com.sample.DroolsTest.Message;
>
>     public class FusionMain {
>
>       public static final void main(String[] args) {
>
>
>
>
>         try {
>
>           KnowledgeSessionConfiguration config =
>     KnowledgeBaseFactory.newKnowledgeSessionConfiguration();
>           config.setOption( ClockTypeOption.get("realtime") );
>           KnowledgeBase kbase;
>           kbase = readKnowledgeBase();
>           final StatefulKnowledgeSession ksession =
>     kbase.newStatefulKnowledgeSession();
>
>           WorkingMemoryEntryPoint myStream =
>     ksession.getWorkingMemoryEntryPoint("My Stream");
>
>           Thread t = new Thread(new Runnable(){
>
>             @Override
>             public void run() {
>               ksession.fireUntilHalt();
>
>             }
>
>           });
>
>           t.start();
>
>           for (float x = 0.0f; x < 20.0f; x++){
>             DataReading dr = new DataReading("Reading " + x, x);
>             myStream.insert(dr);
>           }
>
>
>         } catch (Exception e) {
>           // TODO Auto-generated catch block
>           e.printStackTrace();
>         }
>
>       }
>
>       private static KnowledgeBase readKnowledgeBase() throws Exception {
>         KnowledgeBuilder kbuilder =
>     KnowledgeBuilderFactory.newKnowledgeBuilder();
>         kbuilder.add(ResourceFactory.newClassPathResource("Sample.drl"),
>     ResourceType.DRL);
>         KnowledgeBuilderErrors errors = kbuilder.getErrors();
>         if (errors.size() > 0) {
>           for (KnowledgeBuilderError error: errors) {
>             System.err.println(error);
>           }
>           throw new IllegalArgumentException("Could not parse
>     knowledge.");
>         }
>         KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
>         kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
>         return kbase;
>       }
>
>
>     }
>
>     With the following rule in the sample.drl file:
>
>     package com.sample
>     import com.sample.DroolsTest.Message;
>     import java.util.Date;
>
>     declare DataReading
>         @role( event )
>
>     end
>
>     rule "MyGuidedRule"
>         dialect "mvel"
>         when
>             $dr: DataReading( reading > "10.0" ) from entry-point "My
>     Stream"
>         then
>             System.err.println("Reading: " +  $dr.name
>     <http://dr.name> + " > 10.0 " +
>     System.currentTimeMillis());
>     end
>
>     know I am running fireUntilHalt on a seperate thread as you can
>     see, but
>     events injected fire rules out of order...in fact almost the exact
>     opposite order in which they were inserted to the stream every time:
>
>     Reading: Reading 19.0 > 10.0 1311325346490
>     Reading: Reading 18.0 > 10.0 1311325346491
>     Reading: Reading 17.0 > 10.0 1311325346491
>     Reading: Reading 16.0 > 10.0 1311325346491
>     Reading: Reading 15.0 > 10.0 1311325346491
>     Reading: Reading 14.0 > 10.0 1311325346491
>     Reading: Reading 13.0 > 10.0 1311325346491
>     Reading: Reading 12.0 > 10.0 1311325346491
>     Reading: Reading 11.0 > 10.0 1311325346491
>
>     I want to eventually perform temporal reasoning, but how can I expect
>     that to work if events are not evaluated in the order they were
>     inserted.
>
>     Perhaps I am setting up my session/kb improperly?
>
>     Thanks,
>     Chris
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>
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