In the system being used to define these interfaces, OMG-IDL,
multiple inheritance of interfaces (types) is just fine; there
is no "if" required! It's the same as in Java, or with C++
virtual public inheritance:
interface Element : Node { ... }
interface XMLNode : Node { ... }
interface XMLElement : XMLNode, Element { ... }
Not that there's an "XMLElement" interface defined now.
Don't confuse this with the "single implementation inheritance"
rule that most systems (other than C++) follow.
Now, as for the ECMA Script bindings ... I'm not an expert in
how the DOM WG is mapping IDL to ECMA Script.
- Dave