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RE: CURIEs: A proposal

From: Misha Wolf <Misha.Wolf@reuters.com>
Date: Tue, 27 Jun 2006 14:35:59 +0100
To: public-rdf-in-xhtml-tf@w3.org, semantic-web@w3.org, www-tag@w3.org
Message-id: <A29ADE959C70A1449470AA9A212F5D800228D523@LONSMSXM06.emea.ime.reuters.com>

Hi Dan,

Many thanks for the very detailed info.  See further comments inline.

>>7a  the syntactic constraints (if any) on the prefix and suffix.
>>
>>    XMLNS    : prefix/suffix = NCNAME; prefix can be omitted
>>    XHTML    : prefix = NCNAME; suffix = IRI; prefix can be omitted
>>    NewsML 2 : prefix/suffix = NCNameChar+
>>    SPARQL   : ?
> 
> Item 1 of the list from which this 7a comes is
>> "1   We agree on a generic syntax and generic rules for Compact 
>>      URIs (CURIEs) in attribute values."
> 
> SPARQL isn't carried in XML, so I'm not sure how the survey applies.

I'll remove the words " in attribute values".

> In SPARQL, names of the form _:xyz are used for something other
> than URI abbreviations. The grammar seems to prohibit prefixes
> from starting with "_". And in both the prefix and the suffix,
> starting with a "." seems to be prohibited.
> For details, see http://www.w3.org/TR/rdf-sparql-query/#rNCNAME_PREFIX

I'll include this info.

>>     RDF/XML  : ?

> RDF/XML doesn't have qnames in content. For elements/attributes,
> it follows XML.

I'll include this info.

>>     N3       : ?
>>     Turtle   : ?

> turtle seems to disallow "." in names altogether. And I don't
> see "_" there either.
> http://www.dajobe.org/2004/01/turtle/#nameChar

I'll include this info.

> The lexical details of N3 are a work in progress; the
> grammar that TimBL maintains says...
> 
> qname
>         
>         (([a-zA-Z_][a-zA-Z0-9_]*)?:)?[a-zA-Z_][a-zA-Z0-9_]*
> 
>   -- http://www.w3.org/2000/10/swap/grammar/n3-report.html
> 
> but I think the code and tests differ. We seem to have
> a test for a non-ascii character in a name, but I can't
> find it in the log of the tests run for the latest release,
> so I'm not sure what it's status is.

I'll include this info.

>>7b  how CURIEs and URIs are distinguished, eg through dedicated 
>>    attributes or through a special syntax.
>>
>>    XMLNS    : ?
>>    XHTML    : Mix of dedicated attributes and special syntax 
>>               ("[a:b]") for non-dedicated attributes
>>    NewsML 2 : Dedicated attributes
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> In SPARQL, N3, and turtle, URI references are written <thusly>,
> and qnames can't have <>s in them.

I'll include this info.

>>7c  the mechanism for specifying the prefix-to-IRI mapping.  The 
>>    mechanism may use information provided out-of-band.
>>
>>    XMLNS    : xmlns attribute
>>    XHTML    : xmlns attribute
>>    NewsML 2 : scheme element
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> RDF/XML follows XML namespaces.
> 
> In turtle and N3, prefixes are declared a la
>   @prefix abc: <http://example/abc#>.
> 
> and in SPARQL it's almost the same except for the
> leading @ and trailing '.', and that the case of
> the keyword doesn't matter:
> 
>   PREFIX abc: <http://example/abc#>

I'll include this info.

>>7d  whether and, if so, how the prefix and suffix are combined to 
>>    form an IRI.
>>
>>    XMLNS    : Left to each language to specify
>>    XHTML    : Plain concatenation, including cases such as:
>>               prefixIRI = http://www.example.com/partial_
>>               suffix    = folder/item
>>               fullIRI   = http://www.example.com/partial_folder/item
>>    NewsML 2 : For vocabularies managed by the IPTC, we're 
>>               considering:
>>                 <vocabIRI>>& "#_" & <code>
>>               or plain concatenation, coupled with vocabIRIs ending 
>>               with "?" or "/" or "#_" 
>>               For vocabularies not managed by the IPTC:
>>                 Left to each vocabulary authority to specify
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> RDF/XML uses plain concatenation, as do SPARQL, turtle, and N3.

I'll include this info.

>>7e  whether the prefix and suffix form a tuple or whether they are 
>>    a compact representation for an IRI.

> 'whether'? They always form a tuple; that's sort of self-evident, 
> no?
> I guess the question is whether the tuple is also specified to be
> an IRI abbreviation.

Syntactically, they always form a tuple, but semantically, not 
necessarily.  In the XHTML case, these pairs give the same result:

   prefixIRI = http://www.example.com/
   suffix    = partial_folder/item

   prefixIRI = http://www.example.com/partial_
   suffix    = folder/item

   prefixIRI = http://www.example.com/partial_folder/
   suffix    = item

and the result is:

   fullIRI   = http://www.example.com/partial_folder/item

I'll tweak the wording.

>>    XMLNS    : Tuple
>>    XHTML    : Compact representation for an IRI
>>    NewsML 2 : Tuple and compact representation for an IRI
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> In RDF/XML, the tuple from XMLNS is used as an IRI abbreviation.
> There are lots of cases where it's useful to round-trip back
> to the tuple, though that's never strictly required.
> 
> Same for SPARQL, turtle, and N3.

I'll include this info, though I'm not sure that RDF/XML, SPARQL, 
turtle, and N3 truly treat the data as a tuple rather than just as 
an IRI abbreviation.

>>7f  whether the dereferencing of the IRI mapped to the prefix is 
>>    required to yield a useful and relevant information resource.
>>
>>    XMLNS    : Not required, but the Architecture of the WWW states:
>>               "The owner of an XML namespace name SHOULD make 
>>               available material intended for people to read and 
>>               material optimized for software agents in order to 
>>               meet the needs of those who will use the namespace 
>>               vocabulary."
>>    XHTML    : Not required; note that the prefix may correspond to a
>>               partial, nonsensical IRI, without the suffix (see 7d)
>>    NewsML 2 : Required
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> The URI mapped to the prefix isn't relevant at the RDF abstract
> syntax level. It's handy to be able to look it up for RDF/XML
> consumers that only know they're looking at XML.

I'll include this info.

>>7g  whether the dereferencing of the IRI built from the prefix and 
>>    suffix (and, possibly, also other building blocks) is required 
>>    to yield a useful and relevant information resource.
>>
>>    XMLNS    : Left to each language to specify
>>    XHTML    : Yes

> Really? Which part of the XHTML spec requires that? Surely
> it's no more required to be available than the target of an 
> href="..."?

I'll insert Shane's clerification.

>>    NewsML 2 : For vocabularies managed by the IPTC: MUST
>>               For vocabularies not managed by the IPTC: SHOULD
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> It's a best practice in RDF (i.e. RDF/XML and SPARQL and N3 and 
> turtle).

I'll include this info.

>>7h  whether any fragment identifiers in these IRIs are required to 
>>    be legal XML names.
>>
>>    XMLNS    : Outside the scope of the spec
>>    XHTML    : Outside the scope of the spec
>>    NewsML 2 : Yes
>>    SPARQL   : ?
>>    RDF/XML  : ?
>>    N3       : ?
>>    Turtle   : ?

> RDF doesn't put any constraints on fragments.

I'll include this info.

Thanks.

Misha
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Received on Tuesday, 27 June 2006 13:37:03 GMT

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