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Re: sketch of new proposal reagle-01 reagle-02 tex-??

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Wed, 12 Mar 2003 11:07:26 +0000
To: Jeremy Carroll <jjc@hpl.hp.com>
cc: w3c-rdfcore-wg@w3.org
Message-ID: <4782.1047467246@hoth.ilrt.bris.ac.uk>

>>>Jeremy Carroll said:
> At the telecon I was actioned to bring a new proposal on the reagle issues.
> This is a sketch intended to allow members of the WG who were absent at the 
> telecon to comment. I will expand the details later (not on semantics - which
> I intend to leave to Pat's discretion)
> Changes:
>   with comments
>   c14n done in syntax doc
>   implementation note added to concepts
> Syntax 
> =====

7.2.17 http://www.w3.org/TR/2003/WD-rdf-syntax-grammar-20030123/#start

> +  7.2.17 changed to indicate that exc-canonicaliztion with comments and with
> empty  InclusiveNamespaces PrefixList. is performed.
> +   add new link from part where it is said that use of N-Triples is not 
> required to implementation note in concepts

I don't understand this.  Link from this section?  To the
IMPLEMENTATION NOTE you propose below.

There is a bullet point in section 6

Could you add some URLs to what you want to change?

> Concepts
> =======

In http://www.w3.org/TR/2003/WD-rdf-concepts-20030123/#section-XMLLiteral

> +  change lexical space of rdf:XMLLiteral to be strings that are root element
> content of canonical XML documents

how about: 
  strings that are the contents of the root element of canonical XML documents

> +  change mapping of rdf:XMLLiteral to be a string concatenation
> '<rdf-wrapper xml:lang="'
> lang
> '">'
> string
> '</rdf-wrapper>'

I should note that I've answered several people who wanted to know
where the rdf-wrapper element was defined, so maybe a more prominent
stating that this is arbitrary might help.

> +  add implementation note at end of abstract syntax section
> This section describes an *abstract* syntax which describes
> equality of literals and equivalence of graphs. This is the
> syntax over which the foraml semantics are defined.
> Implementations are free to represent literals and RDF graphs in 
> any other equivalent form. As a first example: language tags may be
> represented in their original case, and language tag comparison would
> then be a case insensitive string comparison. As a second example:
> literals with datatype rdf:XMLLiterals can be represented in a non-canonical

<tt>rdf:XMLLiteral</tt>s I assume

> format, and canonicalization performed during the comparison between two
> such literals. In both of these examples, the comparisons may be 
> being performed either between syntactic structures or
> between their denotations in the domain of discourse.
> Implementations that do not require such comparisons can
> hence be optimized.

This note reminds me, do we canonicalize the language strings to
lower/uppercase?  I know it has been suggested (from I18N WG?) that
it is best to preserve this for people but given there is no other
variation allowed in literal or URI canoncalization, I think we
should consider picking one and requiring it.

> Semantics
> ========
> + follow concepts as appropriate
>   (Note: there is still rdf:XMLLiteral as a special case because even though 
> the mapping is simplified, it is still there, and it still requires the lang 
> tag as an argument).
> ********************
> The first example with language tag case is intended to:
> - be easy to understand
> - partially address an issue raised by Tex Texin (possibly on behalf of I18N 
> WG), no ID yet.

Pointer to email?

> The second example is intended to address part of my action.

Where are these first & second examples?

> ********************
> The suggested wording for the lexical and value spaces of rdf:XMLLiteral in 
> concepts  permits the following:
> <rdf-wrapper xml:lang="">
>   <eg:a xmlns:eg="eg:a" xmlns:unused="eg:b"></eg:a>
> </rdf-wrapper>
> This does not correspond to any RDF/XML document.
> A more complicated wording:
> [[
> The value space
>  is the set of all XML documents that: 
> + Have root element tag: <rdf-wrapper>

This is the point that has confused some people, looking for a
definition of rdf-wrapper.

> + Have no attributes on the root element other than xml:lang
> + are Canonical XML [XML-C14N] (with comments).
> ADD:
> ****
> + which are unchanged when transformed using the exclusive canonicalization
> with comments and with empty namespace prefix list
> ****
> OR
> ******
> + which have no namespace declarations that are not visibly used [EXC-C14N]
> ******
> ]]
> could avoid this.

The latter seems clearer, rather than defining the condition in terms
of yet another transformation.

> (The example document would have the declaration for xmlns:unused deleted by 
> such a transform, and hence be excluded from the datatype).
> Is that better or worse?

If you mean the three line <rdf-wrapper> above, then I'm not sure
what to answer.  If we are going for a tighter definition of what is
canonical, then some XML will be transformed to canonical form, so I
can't really say better or worse.  The group(s) that created these
canonicalization transformations surely considered this.

Received on Wednesday, 12 March 2003 06:08:51 UTC

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