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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: equivalentTo vs. XSLT
 Jonathan Borden wrote, > Miles Sabin wrote: > > I don't believe that any logic that's likely to be interesting in > > this kind of context is decidable. Let's face it, your semantic web > > reasoner is going to have to do the same job as the transform, so > > how could it be guaranteed to terminate in finite time if the > > transform can't be? > > Ahh but that is _exactly_ the point. DLs are carefully crafted > exactly so as to be able to give you this guarantee. DL is _not_ > Turning complete. The problem of classification does not require a > Turing complete processor. Ahh, but it's exactly _my_ point too ;-) The fact that DLs are so carefully crafted means that their scope is pretty drastically limited. I think that it's quite likely that this lack of expressiveness will cause major headaches in many, many contexts: things which can be expressed quite deftly with arithmetic or a sprinkling of second-order machinery, can be either inexpressible or explosively long-winded in weaker systems. How would you say "X has the same properties as Y, apart from P" or "X has twice the number of widgets as Y" in a DL? Aren't those the kinds of things you'd want to be able to say easily when expressing a mapping between ontologies? Nb. I'm _not_ saying that DLs aren't useful ... only that the translation from an intuitive understanding (which is very likely to be riddled with arithmetic and second-orderisms) of a mapping problem to a functionally equivalent DL rendering is often going to be distinctly non-trivial. In those cases you might well want to trade off decidability for expressive power. Cheers, Miles 
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