code: public void setGlobalVariable(String name, Element value, boolean finalFlag) {
  
  		assert (name != null);
  
  		// Either modify an existing value (with appropriate checks) or add a
  		// new one.
  		if (globalVariables.containsKey(name)) {
  
  			GlobalVariable gvar = globalVariables.get(name);
  			gvar.setValue(value);
  			gvar.setFinalFlag(finalFlag);
  
  		} else if (value != null) {
  			GlobalVariable gvar = new GlobalVariable(finalFlag, value);
  			globalVariables.put(name, gvar);
  		}
  	}
docs: Set the variable to the given value. If the value is null, then the
  variable will be removed from the context.