[rules-users] Looking up values in WHEN block

[Wolfgang Laun]

It's generally not a good idea to use globals in rules.

I suggest that you use a simple
  class MaxSymptoms {


On 25 June 2010 12:43, Dobedani <dobedani at gmx.net> wrote:

>
> Dear All,
>
> I'm trying to develop rules which will help to analyse incoming reports of
> disease related symptoms. I have found a way to fill a HashMap with maximum
> allowable values specific for various symptoms. I would like to lookup the
> relevant value any time a symptom comes in. In the first place, I'm trying
> to check whether (1) the HashMap's keySet contains the found symptom i.e.
> in
> the WHEN block - but it does not work as expected. Let alone (2) that I can
> lookup the maximum allowable value and check whether it has been exceeded!
> It is strange to me that the result of both "actions" can however be
> printed
> out in the THEN block. How to do this? Any help will be appreciated.
>
> Kind regards, Dobedani
>
>
> Here's some of my Java code:
> public class Symptom {
>    private String name;
>    private String location;
>    private int period;
>    private int numCases;
>
>    // getters and setters ...
> }
>
> And:
> KnowledgeBase kbase = readKnowledgeBase();
> StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
> java.util.Map maxSymptoms = new java.util.HashMap<String, Integer>();
> ksession.setGlobal("maxSymptoms", maxSymptoms);
>
> Now, some of the code from my DRL file:
> import Symptom;
> global java.util.Map maxSymptoms;
>
> function void prepareMap(java.util.Map map) {
>    if (map.size() == 0) {
>        map.put("fever", 20);
>        map.put("diarrhoea", 30);
>    }
> }
>
> rule "Initialisation"
>    salience 100
>    when
>        eval(true);  // always!
>    then
>        prepareMap(maxSymptoms);
> end
>
> rule "Number of cases with particular symptom observed"
>    dialect "mvel"
>
>    when
>        #conditions
>        Symptom( symptomName : name );
>        eval(maxSymptoms.keySet() contains symptomName);
>        #Symptom( numCases > maxSymptoms[symptomName] );
>    then
>        #actions
>        System.out.println(maxSymptoms.keySet() contains symptomName);
>        System.out.println( maxSymptoms[symptomName] );
>        #System.out.println("Number of cases with " + symptomName + "
> exceeds maximum ")
> end
>
>
> --
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