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Re: Value space of CURIE datatype

From: Shane McCarron <shane@aptest.com>
Date: Tue, 13 Mar 2007 12:11:35 -0500
Message-ID: <45F6DB47.9010504@aptest.com>
To: Steven Pemberton <steven.pemberton@cwi.nl>
CC: Pete Johnston <Pete.Johnston@eduserv.org.uk>, www-html@w3.org, "public-rdf-inxhtml-tf@w3.org" <public-rdf-inxhtml-tf@w3.org>

I concur with Steven's opinion. 

Steven Pemberton wrote:
>
> Good comment. My opinion on this is:
>
>     1. The value space of CURIEs is that of IRIs, since that is (only) 
> what goes over the wire.
>     2. It is the lexical space of Qnames that is a subset of the 
> lexical space of CURIEs.
>
> Best wishes,
>
> Steven Pemberton
>
> On Tue, 13 Mar 2007 16:05:28 +0100, Pete Johnston 
> <Pete.Johnston@eduserv.org.uk> wrote:
>
>>
>> Hi,
>>
>> Thanks to the authors/editors for the work on the CURIE Syntax 1.0
>> document [1]. I have one question/comment.
>>
>> The definition of "datatype" in XML Schema Part 2: Datatypes [2] says:
>>
>> [Definition:]  In this specification, a datatype is a 3-tuple,
>> consisting of a) a set of distinct values, called its *value space*, b)
>> a set of lexical representations, called its *lexical space*, and c) a
>> set of *facet*s that characterize properties of the *value space*,
>> individual values or lexical items.
>>
>> And all the datatypes defined by the XML Schema Part 2 document are
>> defined in those terms.
>>
>> So my questtion is: what is the value space for the CURIE datatype?
>>
>> As far as I can see, the current draft does not specify the value space
>> for the CURIE datatype - though there are "hints" in the text that seem
>> to offer two (mutually exclusive, I think?) possibilities:
>>
>> Option 1: the value space for CURIE is the set of URIs (or IRIs?)
>>
>> This interpretation might be supported by the fact that e.g. the
>> introduction says:
>>
>>> This specification addresses the problem by creating a new data type
>> whose purpose is specifically to allow for the abbreviation of URIs in
>> exactly this way.
>>
>> Also section 4 says:
>>
>>> In all cases a parsed CURIE will produce a IRI.
>>
>> However, if the value space is the set of IRIs, then I think the
>> assertion in section 4 that QNames are a subset of CURIEs is incorrect.
>> According to XML Schema Part 2, the QName datatype is defined as [3]:
>>
>> [Definition:]   QName represents XML qualified names. The *value space*
>> of QName is the set of tuples {namespace name, local part}, where
>> namespace name is an anyURI and local part is an NCName. The *lexical
>> space* of QName is the set of strings that *match* the QName production
>> of [Namespaces in XML].
>>
>> If the value space of CURIE is the set of IRIs, while it's true that the
>> lexical space of QName is a subset of the lexical space of CURIE, then,
>> given the differences in the value spaces, I don't think it's correct to
>> say that QNames are a subset of CURIEs.
>>
>> Option 2: the value space for CURIE is a set of tuples {IRI, ifragment}
>>
>> This interpretation might be supported by the fact that e.g. the
>> introduction says:
>>
>>> This type is called a "CURIE" or a "Compact URI", and QNames are a
>> subset of this.
>>
>> Also section 4 says:
>>
>>> CURIEs can be used in exactly the same way that QNames are, with the
>> modification that the format of the strings before and after the colon
>> are looser.
>>
>> However, if the value space of CURIE is this set of tuples, then I think
>> the document needs to be clearer that the interpretation of this tuple
>> as a single URI or IRI (by concatenation of the two components of the
>> tuple) is _not_ a characteristic of the datatype itself, but a choice of
>> some other specification in which the CURIE datatype is deployed
>> (similarly, for example, to the case for the interpretation of _some_
>> QNames in RDF/XML). And so I think it is probably inaccurate to say "In
>> all cases a parsed CURIE will produce a IRI."; that is true only if some
>> specification other than the CURIE datatype specification licences that
>> further mapping of the tuple to an IRI by concatenation.
>>
>> I had a (very brief) exchange with Mark about this on the
>> public-rdf-in-xhtml-tf list a while back, and, TBH, I should probably
>> have pursued the question a bit harder back then! I think Mark's reply
>> to me [4] was confirming that the value space of CURIE was a set of
>> tuples, not a set of URIs/IRIs i.e. Option 2 above.
>>
>> I guess my point is that whatever the value space of the CURIE datatype
>> is, the document which describes/defines it should be clear about what
>> that value space is, and (to me) the current draft still seems slightly
>> ambiguous on this point.
>>
>> (I say this as someone who is interested in making use of CURIEs, I
>> should add!)
>>
>> Cheers
>>
>> Pete
>>
>> [1] http://www.w3.org/TR/2007/WD-curie-20070307/
>> [2] http://www.w3.org/TR/xmlschema-2/#datatype
>> [3] http://www.w3.org/TR/xmlschema-2/#QName
>> [4]
>> http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2005Nov/0013.
>> html
>>
>> ---
>> Pete Johnston
>> Technical Researcher, Eduserv Foundation
>> Web: http://www.eduserv.org.uk/foundation/people/petejohnston/
>> Weblog: http://efoundations.typepad.com/efoundations/
>> Email: pete.johnston@eduserv.org.uk
>> Tel: +44 (0)1225 474323
>>
>>
>>
>
>

-- 
Shane P. McCarron                          Phone: +1 763 786-8160 x120
Managing Director                            Fax: +1 763 786-8180
ApTest Minnesota                            Inet: shane@aptest.com
Received on Tuesday, 13 March 2007 17:12:47 GMT

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