Re: URI ends with #

Section 0.1 of RDF Semantics says:  "There are several aspects of
meaning in RDF which are ignored by this semantics; in particular, it
treats URI references as simple names, ignoring aspects of meaning
encoded in particular URI forms [RFC 2396] and does not provide any
analysis of time-varying data or of changes to URI references. It does
not provide any analysis of indexical uses of URI references, for
example to mean 'this document'."

Section 1.2 goes on to say: "The semantics does not assume any
particular relationship between the denotation of a URI reference and a
document or Web resource which can be retrieved by using that URI
reference in an HTTP transfer protocol, or any entity which is
considered to be the source of such documents. Such a requirement could
be added as a semantic extension, but the formal semantics described
here makes no assumptions about any connection between the denotations
of URI references and the uses of those URI references in other protocols."

IOW, RDF doesn't associate any special meanings with various URI forms,
including those with empty fragids.  They are simply names, to be
compared as strings (as noted already). RDF, strictly speaking, doesn't
really include the concept of a "document" per se;  the closest thing is
a "graph".  I think phrases like "RDF document" in various specs should
be understood as meaning "some document that contains RDF statements"
(such as an RDF/XML document;  since RDF/XML is XML, it's legitimate to
talk about "documents" in this case, since XML formally defines what a
"document" is).  The RDF Concepts material referred to here doesn't say
that there *are* "RDF documents" corresponding to the URIrefs it's
talking about;  it says you can reconcile the RDF and RFC 2396 uses of
fragids by imagining that there such documents.

--Frank

Jeremy Wong üÜûòÕá wrote:
> 
> "Two RDF URI references are equal if and only if they compare as equal, 
> character by character, as Unicode strings" [1]
> 
> It is actually a Simple String Comparison [2].
> 
> Another point is that, the meaning of a fragment is scheme dependent.
> 
> I don't know whether an empty fragid reference the entire document either.
> 
> 
> 
> Regards,
> Jeremy Wong üÜûòÕá
> 
> 
> -- 
> [1] http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#dfn-URI-reference
> [2] RFC3986, Section 6.2.1.  Simple String Comparison
> 
> 
> ----- Original Message ----- From: "Chris Purcell" <cjp39@cam.ac.uk>
> To: "Jeremy Wong üÜûòÕá" <jeremy@miko.hk>
> Cc: <semantic-web@w3.org>
> Sent: Tuesday, June 07, 2005 8:05 PM
> Subject: Re: URI ends with #
> 
> 
>> Does an empty fragid reference the entire document? That would mean 
>> <http://www.example.org/#> is the same URI as <http://www.example.org/>.
>>
>> Chris
>>
>>> Thanks Arjohn,
>>>
>>> I am actually writing a serializer that put me into the question. I 
>>> am sure that I should throw an exception for this case and those 
>>> cases mentioned in the Serialising section.
>>>
>>>
>>> Regards,
>>> Jeremy Wong üÜûòÕá
>>>
>>>>> Consider the rdf:Property http://example.org/#
>>>>>  in Notation 3, I can write a triple as
>>>>> <http://example.org/A> <http://example.org/#> <http://example.org/B> .
>>>>>  in RDF/XML, how can I write the triple? Let me try...
>>>>>  <Description xmlns:ex="http://example.org/#" 
>>>>> rdf:about="http://example.org/A">
>>>>>   <ex: rdf:resource="http://example.org/B" />
>>>>> </Description>
>>>>>  However, "ex:" does not match the definition of Qualified Names 
>>>>> [1] and the character "#" is not an NCNameChar [2]. I don't have 
>>>>> any idea to express the predicate which its URI ends with #. Any 
>>>>> suggestion?
>>>>
>>>>
>>>> This triple cannot be serialized in RDF/XML. See [1] for a short
>>>> discussion on the serialization of RDF in XML. The only way to 
>>>> serialize
>>>> such a triple is to use one of the other formats (N3, Turtle, ...).
>>>>
>>>> Arjohn
>>>>
>>>> [1] http://www.w3.org/TR/rdf-syntax-grammar/#section-Serialising
>>
>>
>>
> 
> 
> 
>

Received on Tuesday, 7 June 2005 17:30:39 UTC