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Re: FAQ: What's Wrong with Multiple Inheritance? (was Re: RDF Concepts Reference)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Thu, 18 Jan 2001 20:38:46 +0000
To: uche.ogbuji@fourthought.com
CC: Dan Brickley <Daniel.Brickley@bristol.ac.uk>, Dennis van der Laan <LaanD@vertis.nl>, www-rdf-interest@w3.org
Message-ID: <4149.979850326@tatooine.ilrt.bris.ac.uk>
>>>uche.ogbuji@fourthought.com said:
> It seems that ever since Java came out crowing for some odd reason
> that it had "fixed" C++'s use of MI, the orthodoxy has become that
> multiple inheritance is bad, but I think this is nonsense.

There are whole newsgroups where you can have fun with that flame war.

> Certainly in RDF it makes the most eminent sense.  Inheritance is a simple 
> arc, and I don't see how the cardinality of that particular arc hampers the 
> quality of the expression or implementation in any way.

In off list discussions, Dennis and I emailed further about my
comment and I would like to restate it in this way - RDF has a class
and type system that is neutral on how the class graph is arranged.
There is only one restriction - no loops of subClasses are allowed.
i.e. hierachies, trees including multiple inheritance are allowed.

Neither of the standards really mention inheritance at all - RDF M&S
mentions it once in the introduction without much indication of what
that means.

As an implementer, I just need to know - what typing / classing is
allowed and then I can try to work out how best to optimise it.  In
this case, since there are no loops, a partial ordering is one
possible method.

I've reworded some of my original comments in
  http://www.redland.opensource.ac.uk/notes/concepts.html
and added more explanations.

Dave
Received on Thursday, 18 January 2001 15:39:02 GMT

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