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RE: Combo Proposal xmlsch-03 xmlsch-04 pfps-13

From: <Patrick.Stickler@nokia.com>
Date: Fri, 2 May 2003 10:42:15 +0300
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B01B90D5E@trebe006.europe.nokia.com>
To: <jjc@hpl.hp.com>, <w3c-rdfcore-wg@w3.org>



> -----Original Message-----
> From: ext Jeremy Carroll [mailto:jjc@hpl.hp.com]
> Sent: 30 April, 2003 10:45
> To: w3c-rdfcore-wg@w3.org
> Subject: Combo Proposal xmlsch-03 xmlsch-04 pfps-13
> 
> 
> 
> 
> All three of these issues concern the relationship between 
> RDF datatyping and 
> XML Schema datatypes.
> 
> xmlsch-03 concerns the terms "lexical mapping" "datatype mapping" 
> "lexical-to-value mapping"
> 
> xmlsch-04 concerns the phase "zero or more" which permits 
> values in the value 
> space to have no corresponding lexical forms in the lexical 
> space. This was 
> primarily intended for XML Schema Union datatypes.
> 
> pfps-13 concerns facets in general
> 
> I suggest we accept the need for clarification but make no 
> substantive 
> changes. (It is not clear that any of the comments were 
> seeking substantive 
> change).
> 
> I observe that
>  RDF datatyping uses a simplification of the datatyping model 
> in XML Schema
> 
> and hence PROPOSE
>  - xmlsch-03 - we globally use the term lexical-to-value 
> mapping instead of 
> datatype mapping or any other term
>  - xmslch-04 - we do not change the definition of value space 
> but add a note 
> clarifying the relationship with XML Schema datatypes.
>  - pfps-13 is addressed by the same note (very end of this message)
> 
> specifically:
> 
> OLD TEXT:
> [[
> RDF uses the datatype abstraction defined by XML Schema Part 
> 2: Datatypes 
> [XML-SCHEMA2], and may be used with any datatype definition 
> that conforms to 
> this abstraction, even if not actually defined in terms of XML Schema.
> 
> A datatype mapping is a set of pairs whose first element 
> belongs to the 
> lexical space of the datatype, and the second element belongs 
> to the value 
> space of the datatype:
> 
> + Each member of the lexical space is paired with (maps to) 
> exactly one member 
> of the value space.
> + Each member of the value space may be paired with any 
> number (including 
> zero) of members of the lexical space (lexical 
> representations for that 
> value).
> ]]
> 
> NEW TEXT:
> [[
> The datatype abstraction used in RDF is intended for use with 
                                          ^^^^^^^^^^^^^^^^^^^^^^
> XML Schema Part 2: Datatypes [XML-SCHEMA2]. 

Please change this to something akin to

"The datatype abstraction used in RDF is compatible with
 XML Schema Part 2: Datatypes..."

> A datatype consists of a lexical space, a value space and a 
> lexical-to-value 
> mapping.
> 
> A lexical-to-value mapping is a set of pairs whose first 
> element belongs to 
> the lexical space of the datatype, and the second element 
> belongs to the 
> value space of the datatype:
> 
> + Each member of the lexical space is paired with (maps to) 
> exactly one member 
> of the value space.
> + Each member of the value space may be paired with any 
> number (including 
> zero) of members of the lexical space (lexical 
> representations for that 
> value).

OK.

> A datatype is identified by a URI.

Should we say "denoted" rather than "identified" (given the
current bruhaha about what "identify" means...?

> RDF be used with any datatype definition that conforms to this
> abstraction, even if not defined in terms of XML Schema.

Typo? "RDF *may* be used..."

> NOTE: When the datatype is defined using XML Schema:
> + All values correspond to some lexical form, either using
> the lexical-to-value mapping of the datatype or if it is a union
> datatype with a lexical mapping associated with one of the member
> datatypes.
> + XML Schema facets remain part of the datatype 

Should we rather say "part of the datatype definition". It is not
clear (to me at least) that the facets are part of the datatype,
in the same way as e.g. the lexical/value spaces, etc.)

Rather, the facets serve to define what those lexical/value spaces are
and are mechanisms of the definition/interpretation of the datatype,
not of the datatype itself.

This is demonstrated by the fact that the same datatype can be 
defined in various ways using various XML Schema means, such as
defining xsd:int using only a regular expression defining the
lexical space rather than min/max values constraining the value
space. Thus, facets are part of the definition of the datatype,
not of the datatype itself, and RDF is concerned only with what
is part of the datatype (the lexical/value spaces and L2V mapping).
If facets are used to define the datatype, that is irrelevant
to RDF.


> and are used 
> by the XML 
> Schema mechanisms that control the lexical space and the value space; 
> however these facets cannot be accessed by any standard 
> mechanism within RDF.

Right.

Patrick
Received on Friday, 2 May 2003 03:42:20 EDT

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