[rules-users] Question about in XML: literal-restriction on "null" value

[Christina Lau]

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 

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