glib abstract class vs interface

["Kuang-Chun Cheng" <kcc1967 gmail com>]

Hi,

I'm recently study GObject and hope someone can explain
the difference between

Abstract class defined by G_DEFINE_ABSTRACT_TYPE
and interface.

I think if I use G_DEFINE_ABSTRACT_TYPE to create a
class and define all member functions pointer to NULL (pure
virtual) without implementation, then I will have an interface.

So why GType introduce a new type called INTERFACE.
What kind of new features are introduced in GType's interface ?


Thanks
KC