W3C home > Mailing lists > Public > www-tag@w3.org > February 2008

Re: On the context sensitivity of the QName Schema Datatype

From: <noah_mendelsohn@us.ibm.com>
Date: Fri, 15 Feb 2008 17:02:23 -0500
To: ashok.malhotra@oracle.com
Cc: connolly@w3.org, www-tag@w3.org
Message-ID: <OF3D1821B2.8417C551-ON852573F0.007832EC-852573F0.0078FC94@lotus.com>

Ashok Malhotra wrote:


> 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.

The quote from Dan in the minutes, admittedly unapproved as yet, is: 
"QName is inconsistently defined in Schema".  Also, going back to the IRC 
log, when Dan queued himself to discuss this, he did it by saying:

"<DanC_lap> q+ to note that the QName datatypte doesn't fit XML Schema's 
definition of a datatype"

While you're right that I'm not quite sure Dan used the word 
"contradictory", as I implied in my email, he at least said that the 
Recommendation was "inconsistent".  In short, I thought he quite clearly 
said that he felt that the definition of QName in XSD did not hold up, 
because of his feeling that lexical-to-value mappings should be context 
independent functions (as in fact, strictly, all true mathematical 
functions are I believe).  Another way to put this, though Dan didn't say 
it this way, is that the mapping for QName is not lexical->value, but 
rather (lexical + in scope prefixes) -> value.

Noah

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------








ashok malhotra <ashok.malhotra@oracle.com>
02/15/2008 03:11 PM
Please respond to ashok.malhotra
 
        To:     noah_mendelsohn@us.ibm.com
        cc:     connolly@w3.org, www-tag@w3.org
        Subject:        Re: On the context sensitivity of the QName Schema 
Datatype


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?

Ashok

noah_mendelsohn@us.ibm.com wrote:

>Dan, 
>
>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 
>values.
>    * 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.
>
>Noah
>
>[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
>1-617-693-4036
>--------------------------------------
>
>
>
>
>
> 
>


-- 
All the best, Ashok
Received on Friday, 15 February 2008 22:01:47 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 12:47:52 GMT