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LC: Opposing OWL/XML format

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Mon, 26 Jan 2009 18:56:07 +0000
Message-Id: <9926856B-8AF7-4F74-89DC-6C3AEE607EC9@cs.man.ac.uk>
To: W3C OWL Working Group <public-owl-wg@w3.org>

http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/ 
0036.html

My responses:

Please note that the XML syntax is not primarily justified in terms  
of its relation to the functional syntax. Rather it is independently  
motivated and follows the functional syntax style in order to  
simplify use, learning, specification, etc. In other words, if one is  
going to have an XML syntax, there needs to be special reason to  
*depart* from the functional syntax. There is no such reason.

The motivation for the XML Syntax is better integration with the huge  
XML infrastructure, toolchain, and better accessibility for the XML  
savvy user base. For example, RDF/XML, practically speaking, is not  
XML Schema-able. Thus, it's difficult, or impossible!, to use OWL in  
WSDL based web services in a type sensible way. For example:
	<http://www.w3.org/mid/200710311232.31360.matthew.pocock@ncl.ac.uk>

With a Schema-able serialization, it is possible and practical to use  
generic XML tools. I, for example, use oXygen heavily and get things  
like auto-completion for free.

Writing useful XPath, XSLT, XQuery and CSS is prohibitively difficult  
for RDF/XML, while straightforward for OWL/XML. It is impossible,  
afaik, to do schema aware queries over RDF/XML (i.e., query for all  
axioms, or all class axioms, without having to do a union query), but  
straightforward against OWL/XML.

Many organizations are heavily invested in XML tooling and training,  
thus it behooves us to do reasonable outreach.

"""We also don't see how the introduction of
two serialisation syntaxes (RDF-XML and non-RDF-XML) can make life
easier for developers. Arguably the non-RDF-XML syntax is easier to
handle, but it is mandatory for tools to implement the RDF-XML syntax,
so it's just additional burden."""

OWL/XML actually reduces the burden of development for a large class  
of developers --- those of XML centric tools. So, we have to be a  
little careful about how we measure burden.

Secondly, there's already an open source toolkit (the OWL API) and  
web service:
	<http://owl.cs.manchester.ac.uk/converter/>


"""Also, introducing the non-RDF-XML syntax breaks upwards  
compatibility:
Without any modification, many OWL1 tools will be able to parse all of
OWL2 in  the RDF-XML syntax and most likely even make some semantic  
sense
of it, while the same OWL1 tools will barf at (or at best entirely
ignore) the same OWL2 ontologies when expressed in the non-RDF-XML
syntax."""

Given the OWL API and web based converter,  it's not difficult for  
developers to add it in or users to do the conversion themselves  
(after all, this is the case with Turtle right now). We expect  
further translators (e.g., XSLT or XQuery based) to emerge during CR.  
Finally, if there is significant use of it, we imagine major of OWL  
tools will be happy to add a fairly easy to parse format to their  
toolkit in exchange for an expanded user base.

"""It is also noticeable that the Features document does not give any
supporting use-cases for the introduction of the new syntax."""

The features document is not in last call and is not complete. We  
shall add the rationales listed above.

"""Summarising: this will be a burden on tool developers, and will break
compatibility."""

We believe that the burden is overstated and highly mitigated by the  
available of open source converters. The benefit to users and  
application developers is very high as is the potential to expand the  
OWL market and generally reach out to the XML community.

"""Finally, it breaks with the widespread semantic-web practice that
triples are the exchange currency."""

First, as OWL/XML has a precise, well speced, and standardized  
translation to triples, it's clear that OWL/XML counts as triples. It  
does not count as RDF/XML, but then, neither does Turtle. Turtle is a  
syntax that appeals to people authoring by hand without tool support.  
OWL/XML appeals to XML people. These are good rationales for having  
these additional syntaxes.

Furthermore, with GRDDL and with RIF (which has only an XML exchange  
syntax, afaik, with no RDF mapping) it seems that this semantic-web  
practice is not a trump. We can depart from it for good reason and we  
have, in this case, good reason.

Finally, it does not make sense to make it non-normative. If we are  
trying to spec things for the XML toolchain, then we should do so  
normatively. Neither RDF/XML nor the RDF triple model satisfy this  
need. Note, that this doesn't displace RDF, but it does better  
connect OWL with the XML world. That's good for the semantic web.

Cheers,
Bijan.
Received on Monday, 26 January 2009 18:52:44 GMT

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