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Re: Value space of CURIE datatype

From: Steven Pemberton <steven.pemberton@cwi.nl>
Date: Tue, 13 Mar 2007 17:29:49 +0100
To: "Pete Johnston" <Pete.Johnston@eduserv.org.uk>, www-html@w3.org
Cc: "public-rdf-inxhtml-tf@w3.org" <public-rdf-inxhtml-tf@w3.org>
Message-ID: <op.to4yrzwesmjzpq@acer3010.parc.com>

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
>
>
>
Received on Tuesday, 13 March 2007 16:29:59 GMT

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