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

From: <uche.ogbuji@fourthought.com>
Date: Thu, 18 Jan 2001 18:43:13 -0700
Message-Id: <200101190143.SAA26100@localhost.localdomain>
To: Arnold deVos <adv@langdale.com.au>
cc: Dan Brickley <Daniel.Brickley@bristol.ac.uk>, Dave Beckett <dave.beckett@bristol.ac.uk>, Dennis van der Laan <LaanD@vertis.nl>, www-rdf-interest@w3.org
> On Fri, 19 Jan 2001 06:18, uche.ogbuji@fourthought.com wrote:
> >
> > OK, here's a question I seem to have to ask very frequently, but to which I
> > never seem to get a useful answer.  What on Earth is wrong with multiple
> > inheritance?
> >
> There is a need to distinguish between code and (data)
>  models on this point.  There is nothing at all wrong with MI in data 
> modelling IMHO.  In code there are issues, for example, the interpretation of 
> repeated inheritance.

Oh, there's a lot more to distinguish than just that.  There is a need to 
distinguish between interitance, subclassing and subtyping (I used to think 
this was a quiddity until I read an excellent research paper the cite of which 
I can't dig up right now).  I point this out because my possibly wrong guess 
is that you're talking about code inheritance but RDF subclassing.

But I think that even in code Multiple Inheritance is not automatically bad.  
One form of inheritance is mixing-in, which does not have the "diamond of 
doom" problems that you're hinting at with the "repeated inheritance" comment.

Basically, MI is a tool.  It can be used well or poorly, but again I await 
anyone who can show that it is axiomatically bad.

However, since all here seem to agree that multiple subclassing in RDF is not, 
after all, a bad thing, I'm happy to drop the matter.


Uche Ogbuji                               Principal Consultant
uche.ogbuji@fourthought.com               +1 303 583 9900 x 101
Fourthought, Inc.                         http://Fourthought.com 
4735 East Walnut St, Ste. C, Boulder, CO 80301-2537, USA
Software-engineering, knowledge-management, XML, CORBA, Linux, Python
Received on Thursday, 18 January 2001 20:43:26 UTC

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