empty fields in SCXML events.

The spec defines a set of standard fields in events, such as sendid, etc., and then defines conditions under which they should be left 'emtpy'.  In the ECMAScript data model, we say that "name,type, sendid, origin, origintype, and invokeid are String values, while data is an Object value."   So what should their values be when they are left 'empty'?  Does the spec need to say something about this, or is it obvious?  (In the XPath data model, I think it is obvious: the relevant element is present, but it has no children.)


-          Jim