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Re: [ontolog-forum] RDF & RDFS (was... Is there something I missed?)

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
Cc: ian@xxxxxxxxxxxxxxxx
From: Chris Mungall <cjm@xxxxxxxxxxxxxxx>
Date: Wed, 4 Feb 2009 16:34:12 -0800
Message-id: <E1072C76-5263-4849-ADE7-BF8BB6CDCD70@xxxxxxxxxxxxxxx>

On Feb 4, 2009, at 1:43 PM, Pat Hayes wrote:    (01)

>> It
>> is essential that the representation is computer interpretable, as
>> interoperability is the goal of IDEAS - still doesn't rule out  
>> barcoded body
>> parts, you'll note.
>>
>> I still can't see RDFS and RDF as anything other than syntax  
>> (sorry, we
>> might have to disagree on this)
>
> You are simply wrong about this. I'm not pulling rank or anything,  
> but RDF/S is pretty tightly described in the W3C specs, which are  
> quite clear on what parts are normative, and the model-theoretic  
> semantics is normative. So for example if you say that  
> rdfs:subClassOf is just syntax, so you will choose to interpret it  
> as the motherOf relation, then you are not using RDFS. You are using  
> RDFS syntax in some other, non-RDFS, way.    (02)


I'm not sure Ian is 100% wrong. Or if he is wrong, then he is at least  
in good company. Where OWL is concerned, it's common to treat RDF as a  
syntax - perhaps just because it simplifies things tremendously. See  
for example:    (03)

"OWL 2 Web Ontology Language: Mapping to RDF Graphs"
        http://www.w3.org/TR/2008/WD-owl2-mapping-to-rdf-20081202/
"This document defines a mapping of OWL 2 ontology into the RDF  
**syntax**, and vice versa. "    (04)

You'll have to forgive us mere mortals for getting confused here; it  
goes on to state "The syntax for triples used in this document is the  
one used in the RDF Semantics [RDF Semantics]" - which links to your  
document, which uses N-triples as the syntax. So is RDF a syntax? Why  
doesn't the OWL document say "defines a mapping of OWL 2 ontology into  
N-triples syntax"?    (05)

There is a separate document for mapping to RDF semantics:
        http://www.w3.org/TR/2008/WD-owl2-rdf-based-semantics-20081202/
"This document provides the RDF-compatible model-theoretic semantics  
for OWL 2, called "OWL 2 Full"    (06)

But this can be ignored if one simply wants to use RDF/XML as a  
transport layer for OWL (which I'm guessing will become less common  
now there is a sensible XML syntax for OWL)    (07)

Now obviously the story is a little more complicated here, and it  
seems that the division between syntax and semantics is not entirely  
agreed upon. But there is nothing to stop Ian defining a similar  
mapping for his language, performing tricks such as making rdf:type  
triples disappear into the ether. I guess you could say that the OWL  
folks are "using RDF syntax (particularly rdf:type) in some other non- 
RDF way" - if so, is that bad?    (08)

Personally I don't really see the point, but I just thought I'd point  
out that Ian isn't in the minority here.    (09)

Cheers
Chris    (010)


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