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Definitions of namespace IRI/prefix added to RDF Concepts (was: Re: Ambiguity of "RDF namespace")

From: Richard Cyganiak <richard@cyganiak.de>
Date: Thu, 10 May 2012 22:49:09 +0100
Message-Id: <3F9CB6CD-667B-4F7B-91E6-F9A2E1424D9C@cyganiak.de>
To: Thomas Baker <tom@tombaker.org>, RDF Working Group WG <public-rdf-wg@w3.org>
Hi Tom, others,

There is a new section in the RDF Concepts introduction called “RDF Vocabularies and Namespace IRIs”:
http://dvcs.w3.org/hg/rdf/raw-file/default/rdf-concepts/index.html#vocabularies

It adds new (informative) definitions for the terms “namespace IRI” and “namespace prefix”, points out that they're useful for abbreviating IRIs, and points out that the term “namespace” on its own has no well-defined meaning in an RDF context.

I'm not quite satisfied with it — it reads a bit like something that belongs into the Primer.

If anyone has ideas how to improve it (including “DELETE!”) then please share. Otherwise I'll revisit it once we have a draft of the Primer.

Cheers,
Richard


On 9 May 2012, at 22:53, Thomas Baker wrote:

> On Wed, May 09, 2012 at 09:49:29PM +0100, Richard Cyganiak wrote:
>>> I accept the analogy, but I'm unsure what you mean by "most of the
>>> sequences in the namespace" not having referents.  If you mean "potential
>>> sequences" then of course that is true.  But "namespace," as I see it being
>>> used, implies a set of IRIs explicitly "declared" by the namespace's
>>> "owner."  
>> 
>> Well, that's not the way I see it. I understand a namespace as the set of
>> *all* IRIs starting with the namespace IRI.
> 
> That seems awfully theoretical, at odds with existing usage of "namespace",
> sloppy and inconsistent though it may be.
> 
>> How about this other approach? There's no such thing as a ?namespace? in RDF.
>> Just avoid the term on its own ? it's a remnant of the old XML baggage. Some
>> of the other related XML terms that came along with it have proven to be
>> useful though: Some RDF syntaxes offer a way of associating ?namespace
>> prefixes? with ?namespace IRIs? in order to abbreviate IRIs; and there's
>> ?namespace documents? which describe the terms in an RDF vocabulary all of
>> whose terms start with the same IRI. The term ?namespace? on its own is just
>> a sloppy way of referring either to such an RDF vocabulary or to a namespace
>> IRI.
> 
> +1 - I like this!  Keep "namespace" as an adjective.  Discourage its use as a
> noun by saying that "namespace" has no formal meaning in RDF and that when used
> informally, usage is inconsistent.  And above all, avoid using "namespace" as a
> noun in the formal specs.
> 
>>>>> Also, the current draft of RDF Concepts 1.1 [1] still says:
>>>>> 
>>>>>  "Vocabulary terms in the rdf: namespace are listed and described in
>>>>>  detail..."
>>>>> 
>>>>>  This suggests that the "rdf: namespace" holds not just any IRIs, but
>>>>>  "vocabulary terms" denoted by IRIs.  
>>>> 
>>>> That's not a valid inference. It says that *some* of the things in the rdf:
>>>> namespace are vocabulary terms. It doesn't say that all of the things in the
>>>> rdf: namespace are vocabulary terms.
>>> 
>>> Strictly speaking, I do not think the sentence says that _all_ of the things
>>> in the rdf: namespace are vocabulary terms.  But it also does not say that all of 
>>> the vocabulary terms in the rdf: namespace are listed and described in detail.
>> 
>> Not sure what your point is.
> 
> Really only that the natural-language sentence can be understood in different
> ways (and mostly by people not attuned to what may be "validly inferred").  But
> I see you have removed the section from Concepts 1.1 for folding into the RDF
> Schema document.
> 
>>> It is not incorrect, then, to use the same IRI both as a namespace IRI
>>> and to denote a vocabulary?
>> 
>> It's not incorrect and it is fairly common practice AFAICT.
> 
> And that's fine with me.  The confusing bit, I think, is that
> 
>    "namespace IRI" = "vocabulary IRI"
> 
> however
> 
>    "namespace" != "vocabulary"
> 
>>>> [[
>>>> An OWL ontology is a formal description of a domain of interest, and can be
>>>> used to describe the terms in an RDF vocabulary and their relationships. OWL
>>>> ontologies can themselves be expressed as RDF graphs, using terms in the owl:
>>>> namespace. OWL is more expressive, but also more complex, than RDF Schema. In
>>>> fact, OWL contains RDF Schema as a simple subset.
>>>> ]]
>>> 
>>> Fine, but that's an OWL ontology.
>>> 
>>> What about "ontology"?  
>> 
>> I won't go anywhere near that question.
>> 
>>> Does "ontology" mean "OWL ontology"?  
>> 
>> I suppose every OWL ontology is an ontology? But obviously there are other kinds of ontologies, and there's ontology as a branch of philosophy.
>> 
>>> Is [1] an ontology?  
>> 
>> It's a (manifestation of an) OWL ontology. Every OWL ontology is an ontology. Therefore, [1] is an ontology.
>> 
>>> Does its use of "owl:equivalentProperty" make it an "OWL" ontology?  
>> 
>> It doesn't need to use any OWL vocabulary to be an OWL ontology. As I said: ?OWL contains RDF Schema as a simple subset.?
> 
> +1 - Okay, I get it.
> 
>> (Strictly speaking, an RDF document doesn't even need to define any classes
>> or properties to be an OWL ontology. *Any* RDF document is a (degenerate) OWL
>> document. But that's just sort of an accident in the way OWL is defined.)
> 
> Also fine.  I do not think this necessarily belongs in RDF 1.1 but I'd love to
> see it clarified _somewhere_.
> 
> Tom
> 
> -- 
> Tom Baker <tom@tombaker.org>
> 
Received on Thursday, 10 May 2012 21:49:40 GMT

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