[SCXML] Access datamodel

[Berg, T.W. (Tom) van den]

I'm still sorting out basics before moving on to some real stuff.
 
I have a simple scxml document with a data model listed below. I execute
my program with a custom action (also shown further below).
 
I have a couple of questions:
 
1) For <assign location="Data(label, 'handle')" expr="'a test value'" />
I get the following error. Why?
 
19-jul-2008 1:15:51 org.apache.commons.scxml.Builtin dataNode
WARNING: Data(): No nodes matching the XPath expression "handle",
returning null
19-jul-2008 1:15:51 org.apache.commons.scxml.model.Assign execute
SEVERE: <assign>: location does not point to a <data> node

2)  Also for <rti:register name="result" expr="Data(label,'name')"/>  I
get an error. Why?
 
19-jul-2008 1:15:51 sc.Register execute
INFO: eval(Data(label,'name'))
19-jul-2008 1:15:51 org.apache.commons.scxml.Builtin dataNode
WARNING: Data(): No nodes matching the XPath expression "name",
returning null
19-jul-2008 1:15:51 sc.Register execute
INFO: <var>: Defined variable 'result' with initial value ''

3) How can I transer the result from rti:register back into the
datamodel's handle field from a) the SCXML document or b) the custom
action?

 
Thanks -- Tom
 
----
 
<?xml version="1.0"?>
<scxml xmlns="http://www.w3.org/2005/07/scxml";
       xmlns:rti="http://rti.actions/CUSTOM";
       version="1.0"
       initialstate="SyncPoint">
 
 <state id="SyncPoint">
  
  <datamodel>
   <data name="label">
    <name>initial</name>
    <handle></handle>
   </data>
  </datamodel>
  
  <initial>
   <transition target="registered"/>
  </initial>
  
  <state id="registered">
   <onentry>
    <assign location="Data(label, 'handle')" expr="'a test value'" />
    <rti:register name="result" expr="Data(label,'name')"/>
    <rti:register name="result" expr="2 + 8"/>
   </onentry>        
   <transition event="confirmed" target="confirmed"/>
   <transition event="error" target="error"/>
  </state>
  
  <state id="confirmed">
   <onentry>
    <rti:confirm name="doConfirm" />
   </onentry>        
   <transition target="end"/>
   <transition event="error" target="error"/>
  </state>
  
  <final id="end"/>
  
  <state id="error"></state>
 </state>
 
</scxml>
 
----
 
public class Register extends Action {

<<... cut ...>>
 
 public void execute(final EventDispatcher evtDispatcher,
  final ErrorReporter errRep, final SCInstance scInstance,
  final Log appLog, final Collection derivedEvents)
  throws ModelException, SCXMLExpressionException {
  
  Context ctx = scInstance.getContext(getParentState());
  Evaluator eval = scInstance.getEvaluator();
  
  ctx.setLocal(getNamespacesKey(), getNamespaces());
  
  appLog.info("eval("+expr+")");
  
  Object varObj = eval.eval(ctx, expr);
  
  ctx.setLocal(getNamespacesKey(), null);
  ctx.setLocal(name, varObj);
  
  appLog.info("<var>: Defined variable '" + name + "' with initial value
'" + String.valueOf(varObj) + "'");
  
  TriggerEvent ev = new TriggerEvent(name + ".change",
TriggerEvent.CHANGE_EVENT);
  derivedEvents.add(ev);
 }
 
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