various issues

Peter Murray-Rust Peter at
Fri Apr 11 19:27:02 BST 1997

Thanks very much - it's becoming clearer, and at least I've got the direction 
correct :-).  But I'm not clear what quantities are inherited...

For discussion assume that the declarations belong to MYDTD

In message <199704111037.GAA00242 at localhost> David Megginson writes:
>   <?ArcBase html?> <?ArcBase math?>

So in C++ terms MYDTD has two base  classes, HTML and MATH.  

>   [notations and entities omitted]
>   <!ELEMENT para ...> 
>   <!ATTLIST para
>     html      NAME    #FIXED "p">

This means that PARA (in MYDTD) inherits properties from P (in HTML).  Does
that mean it automatically inherits the content model and the attributes?
For example, the content model of P is
which expands to 
	(#PCDATA | IMG | BR | EM)*  <!-- several missed out -->
Can PARA assume these or does it have to map each of these (e.g. IMG) onto
	<!ELEMENT image ...>
	<!ATTLIST image
	  html    NAME #FIXED "img>
similarly does PARA have to explicity declare the same attributes as P in HTML?

>   <!ELEMENT fraction ...> 
>   <!ATTLIST fraction
>     math      NAME    #FIXED "frac">
>   <!ELEMENT sym ...> 
>   <!ATTLIST symbol
>     html      NAME    #FIXED "sym" 
>     math      NAME    #FIXED "symbol">
This is - presumably - multiple inheritance in that SYMBOL inherits something
from HTML.SYM and MATH.SYMBOL (though I'm not clear what).  How does the
content of SYMBOL relate to either of its two base classes?


Peter Murray-Rust, domestic net connection
Virtual School of Molecular Sciences

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