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Re: On the context sensitivity of the QName Schema Datatype

From: ashok malhotra <ashok.malhotra@oracle.com>
Date: Fri, 15 Feb 2008 12:11:48 -0800
Message-ID: <47B5F204.60207@oracle.com>
To: noah_mendelsohn@us.ibm.com
CC: connolly@w3.org, www-tag@w3.org

AFAIR, Dan did not say that it was contradictory merely that it was 
different from other datatypes
in that the lexical-to-value mapping is context dependent.   And Dan is 
right, it is context dependent but I dont consider
that a problem.

I'm wondering what our friends in Schema would say if we requested a 
CURIE datatype.
There are clearly problems with the syntax which need to be addressed.
But would they warm to the semantics?


noah_mendelsohn@us.ibm.com wrote:

>On yesterday's TAG call, you said (from the draft minutes at [1]):
>"QName is inconsistently defined in Schema -- abc:xyz can denote two 
>distinct values at two points in a document, which is not consistent with 
>the statement that there is a mapping from lexical to value space."
>So, I thought I'd look at the specificaitons From the published working 
>draft of Schema 1.1 Datatypes [2]:
>"[Definition:]  In this specification, a datatype has three properties:
>    * A ·value space·, which is a set of values.
>    * A ·lexical space·, which is a set of ·literals· used to denote the 
>    * A small collection of functions, relations, and procedures 
>associated with the datatype.  Included are equality and order relations 
>on the ·value space·, and a ·lexical mapping·, which is a function on the 
>·lexical space· onto the ·value space·.
>For some datatypes, notably QName and NOTATION, the mapping from lexical 
>representations to values is context-dependent..."
>So, while you (or maybe I) might prefer that the design were different, I 
>don't think it's fair to imply that the Recommendation is contradictory. 
>It makes quite clear that context-dependent lexical mappings are allowed.
>By the way, the treatment in Schema 1.0 is different, though I think it 
>would be fairer to say that it's loose or underspecified than that it's 
>contradictory.  From [3]:
>"[Definition:]  A lexical space is the set of valid literals for a 
>datatype. "
>Pretty broad, but I don't think the definition of QName is inconsistent 
>with that.  The definition of QName found there is:
>"3.2.18 QName
>[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].
>Note:  The mapping between literals in the ·lexical space· and values in 
>the ·value space· of QName requires a namespace declaration to be in scope 
>for the context in which QName is used. "
>Again, I don't think there's anything that implies context independence 
>for the mapping from lexical to value in general, and the Recommendation 
>is very clear that it's context-dependent for types like QName.
>[1] http://www.w3.org/2008/02/14-tagmem-minutes.html#item01
>[2] http://www.w3.org/TR/xmlschema11-2/#datatype
>[3] http://www.w3.org/TR/xmlschema-2/#lexical-space
>Noah Mendelsohn 
>IBM Corporation
>One Rogers Street
>Cambridge, MA 02142

All the best, Ashok
Received on Friday, 15 February 2008 20:12:54 UTC

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