W3C home > Mailing lists > Public > www-rdf-logic@w3.org > August 2002

Re: Semantics, in particular DAML+OIL semantics

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 15 Aug 2002 21:48:49 +0100
Message-ID: <15708.5041.425272.313578@merlin.oaklands.net>
To: "R.V.Guha" <guha@guha.com>
Cc: www-rdf-logic@w3.org

On August 15, R.V.Guha writes:
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> Ian,<br>
>   <br>
>   &nbsp; &nbsp;I'd like a register a protest of your use of the term "standard logical 
> language". There have been a very large number of symbolic systems, both implemented
> and gedanken, starting from Advice Taker to CycL. Description Logics form
> a small subset of such systems. Many of these symbolic systems either lacked
> the concept of subClassOf, etc. or included them in the domain of discourse.<br>
>   <br>
>   &nbsp;So, please, don't say "standard logical language". Say "standard Description
> Logic based language". <br>

Why pick on description logics? The standard logical languages to
which I refer include modal logics, temporal logics, dynamic logics,
standard predicate logics etc. etc.


>   <br>
>   guha<br>
>  <br>
> <br>
> Ian Horrocks wrote:<br>
> <blockquote type="cite"
>  cite="mid15707.42355.464023.150665@merlin.oaklands.net">
>   <pre wrap="">On August 14, R.V.Guha writes:
>   </pre>
>   <blockquote type="cite">
>     <pre wrap="">Ian,
>  Could you explain how RDF can talk about its own syntax? Which syntax 
> are you referring to, the XML syntax or n-triples?
>  Or are you referring to the RDF allowing statements to be made about 
> classes and predicates ... (that isn't really a syntax issue ...)
>  I am very confused.
>     </pre>
>   </blockquote>
>   <pre wrap=""><!---->
> RDF (or at least RDF schema, which I believe is now to be considered
> part of RDF) gives special meanings to some classes and properties,
> e.g., Class, subClassOf, type. In any standard logical language, these
> would be considered to be part of the syntax of the language, and
> would not be part of the domain of discourse of the language itself -
> in predicate logic I can't say anything about the meaning of AND, OR
> and NOT. In contrast, RDF allows me to extend the meaning of such
> syntax, e.g., by asserting that subClassOf is a subPropertyOf type.
> In RDF itself this can be seen as relatively harmless in the sense
> that it simply constrains the set of possible models, even if the
> intended meaning of such statements is difficult to understand. When
> RDF is extended to a more powerful logic (by giving additional meaning
> to some sets of triples), e.g., one including negation, this feature
> becomes much more problematical and makes it impossible to support
> standard logical entailments (trying to do so makes the language
> inherently paradoxical).
> Ian
>   </pre>
>   <blockquote type="cite">
>     <pre wrap="">guha
> Ian Horrocks wrote:
>     </pre>
>     <blockquote type="cite">
>       <pre wrap="">Unfortunately, I don't see how such studies can resolve the practical
> problems associated with layering OWL on top of RDF, e.g., those
> caused by RDF's ability to talk about its own syntax, and the
> inheritance of this ability by wore expressive languages layered on
> top of it.
> Regards, Ian
>       </pre>
>       <blockquote type="cite">
>         <pre wrap="">thank you
> Guha
>         </pre>
>       </blockquote>
>     </blockquote>
>   </blockquote>
> </blockquote>
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Received on Thursday, 15 August 2002 16:51:22 UTC

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