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Re: LC: Opposing OWL/XML format

From: Ivan Herman <ivan@w3.org>
Date: Tue, 27 Jan 2009 10:33:26 +0100
Message-ID: <497ED4E6.8000006@w3.org>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: W3C OWL Working Group <public-owl-wg@w3.org>
Hi Bijan,

just some comments

- My main message of the answer would emphasize the fact (which actually
the commenter refers to!) that the _only_ required exchange syntax is
RDF/XML. Ie, if a tool or a user does not want to implement and/or use
the OWL/XML syntax, then there is no harm done. The OWL/XML syntax is,
so to say, a cherry on the cake if people want to use it, much like lot
of people use Turtle for RDF instead of RDF/XML for various reasons.
(The only danger for this line of thought is the possible answer that
Turtle is not a recommendation. We may have, in our archives, references
we had on this very issue which led to the resolution of publishing
OWL/XML as a rec and not as a note.)

Ie, it is _not_ a burden on tool developers because they can ignore it
if they want; _not_ a burden on the users because they can also ignore
it if they want!

- You also say

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.

I do not think we should refer to RIF here, simply because the charter
of RIF is very different. RIF explicitly has on its charter rule
dialects that are not bound to RDF at all, (ie, not mappable on RDF).
This line of arguments would probably lead the discussion away from the
main issue... (I actually would have liked to have an RDF mapping of the
RDF/OWL specific part of RIF but the group ran out of steam...)

GRDDL... well, if we had a 'standard' mapping from OWL/XML to RDF/XML
via a GRDDL transformation then this could be a very good argument here
in favour of OWL/XML. And we may have that, right?:-)

- OWL 1 had the OWL/XML format published as a note. Are there practical
data and experiences among tool vendors and users on how widely that was
implemented and used? I must admit I do not know. But if those data were
available and convincing, this could be much more important in this
stage of the discussion than the technical arguments...



Bijan Parsia wrote:
> 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.


Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
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Received on Tuesday, 27 January 2009 09:33:54 UTC

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