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Re: Q to implementers: Resource identifiers - XML Names and/or (concatenated) URIs? (was RE: rdfs.isDefinedBy...)

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Fri, 07 Jun 2002 00:05:50 +0100
To: jeremy <jeremy@jeremygray.ca>
CC: www-rdf-interest@w3.org
Message-ID: <16033.1023404750@tatooine.ilrt.bris.ac.uk>

>>>Jeremy Gray said:
> Setting aside for the moment the whole issue of namespace URIs and their
> potential relation to RDF Schema documents and the network resolution
> thereof I have a question for RDF application implementers out there
> regarding their use of Resource identifiers in the form of XML Names vs.
> concatenated URIs:
> 
> Since it is obvious that the working group(s) responsible for RDF for one
> reason or another (i.e. current charter) are not in a position to properly
> address RDF's current mangled interpretation of Namespaces in XML and other
> identifier-related issues such as:
> 
> - if RDF/XML requires prefixes before each attribute, it is simply not
> Namespaces in XML -compliant XML

I disagree - RDF/XML is now being based on the Infoset and is
perfectly compliant XML.  We use standard off-the self XML parsers
(expat, gnome libxml, Xerxes, ...) and have no problems living as a
separate layer on top of standard XML access mechanisms like SAX
events, the DOM.  Many people use XSLT to process RDF/XML, such as
the W3C news RSS 1.0 feed - see http://www.w3.org/

If you have an example of some RDF/XML that is illegal
XML with XML Namespaces, please include it.


> - the suggested XML Names -> URI concatenation process produces collisions

The XML qnames are used in RDF/XML as abbreviation mechanism for long
URIs, and although collision has been recognised, it has not been
considered a huge problem.  The point is to generate the URI, the
qname used isn't important.

> - the suggested URI -> XML Names splitting method is so flawed as to not be
> responsibly implementable (i.e. you can't generate valid LocalParts by
> splitting on non-Name characters, but can if splitting on non-NCName
> characters. However, using the latter method produces differently invalid
> results, e.g. if splitting
> urn:NewsML:afp.com:20000811:010607144425.x6pxrl6k:1)

Well, the schema and namespace issues which above, you don't want to
discuss, could provide solutions to that.


I'm really not convinced by your claims.

> Without getting into a huge discussion about each of the example bullets
> above (unless you have specific comments regarding their effect on your
> implementation) ...

I think you are pretty wrong; sorry.

> ... and without starting yet another discussion about how simple
> it would be to fix these issues and how many benefits could be reaped from
> their correction if only an RDF 1.1 or some such could be created that
> natively includes the concept of namespaces, I'd like to hear how
> implementers have dealt with these issues in light of the fact that the
> Working Group(s) can't/won't.  ...

I'm an implementor as well as a WG member and editor of the RDF/XML
refactoring draft.

> Are you fully supporting Namespaces in XML in
> your serialization?

Yes, just like RDF/XML does in the original M&S and in the revised syntax.

> ...  Internally? Are you following the WG-recommended
> concatenation and splitting processes? If not, what are you doing instead?

Yes.

> My company, for example, intends to produce behaviour indicative of full and
> correct interpretation of the Namespaces in XML specification so that
> behaviour both inside and outside of our system is consistent. It may not be
> strict RDF, but it has a better chance of producing correct
> results. ...

Can you say what you are doing that is different?  (Strict RDF=Strict
RDF/XML I assume)

> ... Since
> Namespaces exist within our RDF system (once again, NOT for schema
> identification or resolution, just for identifiers), ...

(XML) namespaces aren't in the RDF model, so you are going beyond
what other RDF apps might expect.

You seem to be conflating the XML (Infoset say, which models things
like elements, attributes, namespaces) and RDF model (graph, URIs, no
namespaces).

> ... and since we do expect
> information to flow to and from other systems operating in terms of the
> naive RDF 1.0 + issue tracking interpretation, we may create something
> analogous to the concatenation/stripping process but which is based on a
> list of known namespaces on which splitting/merging can occur when desired
> instead of the current half-baked process. Since those external applications
> will be creating collisions and improperly splitting URIs anyway, we don't
> honestly expect 100% correct integrated behaviour in any case, but will try
> to integrate with them as best as we can.
> 
> How are you addressing Namespaces in XML -related issues in and around RDF?

By using namespace URIs to indicate when to split.

Cheers

Dave
Received on Thursday, 6 June 2002 19:06:00 GMT

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