Dear all, My system is transforming internal data structure to drools rule language XML file. For particular evaluation on a string field, how can I do so happen the evaluating value is one of the keywords? For example, I need to check if keyValue=="null" In rule language in XML, through the XmlDumper, <field-constraint field-name="keyValue"> <literal-restriction evaluator="==" value="null" /> However, this is the same for evaluation of keyValue==null //check if keyValue is null or not Would someone know how to tell the engine the different scenario in rule language XML file, evaluate on the content, and nullable of the field? Thanks a lot for your help -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Question-about-in-XML... Sent from the Drools - User mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users