code: private Map<String,String> createVariableBindings(List<Variable> childVars, SubprocessInstance piplan,
              boolean passDocumentContent)
              throws Exception {
          Map<String,String> parameters = new HashMap<String,String>();
  
          String vn, v;
          for (int k=0; k<childVars.size(); k++) {
              Variable childVar = childVars.get(k);
              if (!allowInput(childVar)) continue;
              vn = childVar.getName();
              if (vn.equals(VariableConstants.REQUEST)) {
                  VariableInstance varinst = getVariableInstance(VariableConstants.REQUEST);
                  v = varinst==null?null:varinst.getStringValue();
              } else if (vn.equals(VariableConstants.MASTER_DOCUMENT)) {
                  VariableInstance varinst = getVariableInstance(VariableConstants.MASTER_DOCUMENT);
                  v = varinst==null?null:varinst.getStringValue();
              } else {
                  Parameter p = this.getParameterBinding(piplan, vn);
                  v = evaluateBindingValue(childVar, p==null?null:p.getStringValue());
              }
              if (v!=null && v.length()>0) {
                  if (passDocumentContent) {
                      if (VariableTranslator.isDocumentReferenceVariable(getPackage(), childVar.getType())
                              && v.startsWith("DOCUMENT:")) {
                          v = super.getDocumentContent(new DocumentReference(v));
                      }
                  }
                  parameters.put(vn, v);
              }
          }
          return parameters;
      }
docs: This method returns variable bindings to be passed into subprocess.
  The method uses the attribute "variables" values as a mapping.
  The binding of each variable is an expression in the Magic Box rule language.
  Example bindings: "var1=12*12;var2=$parent_var.LIST.LN"
  Subclass may override this method to obtain variable binding in other ways.
  
  @param childVars variables defined for the child process
  @param prMgr process manager remote EJB handle
  @param varMgr variable manager remote EJB handle
  @return a map (name-value pairs) of variable bindings
  @throws Exception various types of exceptions