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[LC] Official SVG Tiny Working Draft Comments from W3C RDF in XHTML Task Force

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Thu, 09 Oct 2008 23:06:05 -0400
Message-ID: <48EEC69D.5090608@digitalbazaar.com>
To: SVG WG <www-svg@w3.org>
CC: RDFa mailing list <public-rdf-in-xhtml-tf@w3.org>

The following are official comments from the RDF in XHTML Task Force
related to the latest SVG Tiny Working Draft located here:

http://www.w3.org/TR/SVGMobile12/metadata.html#MetadataAttributes

The comments revolve around the re-use of RDFa attributes in SVG, which
we are very pleased to see, but feel that there should be specific
direction on how those attributes are used.

Re-use of RDFa attributes should follow RDF in XHTML processing rules
---------------------------------------------------------------------

http://www.w3.org/TR/SVGMobile12/metadata.html#MetadataAttributes
"""
SVG includes several attributes that may be placed on any element, for
the use of attribute-based metadata formats. These include the 'class',
'role', 'rel', 'rev', 'about', 'content', 'datatype', 'property',
'resource', and 'typeof'  attributes. ***SVG makes no specific
requirements about the values for these attributes, other than their
particular value data types, such as a string or a space-separated lists
of strings.*** Other specifications, such as RDFa [RDFA], Microformats
[MF] patterns, or ARIA [ARIA] ontologies,
"""

The current text leaves far too much room for mis-use and abuse of the
RDFa attributes. It would be a shame if authors were allowed to
re-define how a non-RDFa parser may use those attributes in such a way
as to directly conflict, or even worse, create ambiguity with regard to
the current RDF in XHTML parser rules. The RDFa task force went to great
lengths to ensure that the RDFa Syntax Processing[1] rules define clear
behavior when RDFa is used in non-XHTML languages.

Please add text clearly stating that if one re-uses the RDFa attributes
that they follow the same processing rules as outlined in the RDFa
Syntax Processing Rules[1].

@rel/@rev values do not necessarily need to be prefixed
-------------------------------------------------------

http://www.w3.org/TR/SVGMobile12/metadata.html#MetadataAttributes
"""
When used with RDFa, the values for the 'rel' and 'rev' attributes must
be a CURIE [RDFA] (i.e., a prefixed string, such as 'cc:license' to
indicate a Creative Commons license), while the values may simply be
from a set of specific keywords for Microformats. These formats may be
used independently, or in combination if the keywords do not clash.
"""

The @rel/@rev values in RDFa can either be a reserved word or a CURIE as
defined in the RDFa Syntax document[2]. Perhaps the SVG Tiny document is
authored to not support reserved words due to a mis-reading or
mis-understanding of the current CURIE specification[3]? The current
specification allows both prefixed and unprefixed "reference only" values:

http://www.w3.org/TR/curie/#s_syntax
"""
curie       :=   [ [ prefix ] ':' ] reference
...
A host language MAY interpret a reference value that is not preceded by
a prefix and a colon as being a member of a host-language defined set of
reserved values. Such reserved values MUST translate into an IRI, just
as with any other CURIE.
"""

We urge the SVG WG to not limit CURIEs and provide a CURIE mechanism as
defined by the CURIE specification. It would make the job of RDFa parser
authors much easier as there are less special cases to consider when
creating their parser. The current language in SVG Tiny requires all
current RDFa parsers to strip out all reserved word processing in order
to conform to SVG+RDFa, which would lead to two increasingly divergent
types of RDFa parsers:

1. Parsers that parse SVG+RDFa 1.0.
2. Parsers that parse "XHTML+RDFa 1.0".

The SVG Tiny document seems to insist that terms must be of the form
"x:y", instead of also allowing things like "license" (note that there
isn't a preceding colon before a reserved word).

We are currently working on a method to specify reserved words that will
not need preceding colons and the current language in SVG Tiny would
prevent that method from being used in SVG Tiny.

Please do one of the following:

* Adopt the current RDFa/CURIE processing rules as-is.
* Define a set of reserved words that should be used in SVG Tiny and
  preserve the functionality provided in the CURIE Specification.
* Do not rule out the ability to use non-colon-prefixed reserved words.

@role should follow rules defined in XHTML 1.1 Role Module
------------------------------------------------------------

This is not an official comment from the RDF in XHTML Task Force and
will probably be mentioned by the XHTML WG. Mark, Shane and Steven were
on todays RDFa telecon and had issues with the lack of specifics as to
how an author could use @role. Just a heads up that they would like to
see it clearly stated that use of @role should follow the specifics
outlined in the XHTML Role Attribute Module[4]. We want to make sure
that authors are not under the false assumption that they can put
whatever they want to in the @role attribute.

Thanks to the SVG WG in advance for consideration of these issues. We
are looking forward to using RDFa-based semantics in SVG Tiny. Keep up
the great work! :)

-- manu

[1] http://www.w3.org/TR/rdfa-syntax/#sec_5.5.
[2] http://www.w3.org/TR/rdfa-syntax/#relValues
[3] http://www.w3.org/TR/curie/
[4] http://www.w3.org/TR/xhtml-role/

-- 
Manu Sporny
President/CEO - Digital Bazaar, Inc.
blog: Bitmunk 3.0 Website Launches
http://blog.digitalbazaar.com/2008/07/03/bitmunk-3-website-launches
Received on Friday, 10 October 2008 03:06:46 GMT

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