various issues

len bullard cbullard at
Fri Apr 11 19:21:11 BST 1997

Digitome Ltd wrote:
> >Peter Murray-Rust writes:
>  > I think I start to understand.  By 'structure' you mean the tree structure
>  > of each DTD?  In which case AFs are a way of providing multiple views of the
>  > same document?
> An AF is like a virtual class in OO-speak. HyTime is a bit like a set of
> virtual class definitions. From these virtual classes you derive your own
> classes (DTDs) that inherit from their super-class(HyTime).
> Multiple inheritance is allowwed. That is, a given DTD can inherit from
> multiple AF super-classes.

This ties back to the thread on CTS where someone was asking about 
why SGML could not inherit.  Someone should explain in terms 
virtual inheritance, and interface and code inheritance, how 
AFs can be adopted by the OOPMen.  That explanation of SGML, 
architectures, and OOP technique is a missing piece of the 
implementation puzzle and a considerable opportunity for a 
college text.

len bullard

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