RE: Presentation Syntax - why?

Jim- 
 
Danny's main point, and I would agree with him, is that creating yet
another syntax doesn't help those of us who are trying to build tools
and field applications on top of either RDF or OWL. Seeing the
Presentation Syntax document made my heart sink, because now I have yet
another interoperability issue to address. The more interoperability
burdens we have to clear, the slower we will be able to build
applications to further adoption. There's a big difference between
supporting yourself with tools to move from N3 to RDF, and having to
support a user community that already has too many ways to express
themselves in RDF. Throwing a stylesheet over the wall just doesn't cut
it.
 
I would agree with you that the process has been a visible one, but
frankly, I feel a bit blindsided myself. 
 
- regards, BPA
 
Bradley P. Allen
President
Siderean Software LLC
5155 West Rosecrans Avenue, Suite 1078
Los Angeles, CA 90250 USA
phone +1 310 491-3424
fax +1 310 379-0231
web www.siderean.com 

-----Original Message-----
From: www-rdf-logic-request@w3.org [mailto:www-rdf-logic-request@w3.org]
On Behalf Of Jim Hendler
Sent: Tuesday, June 17, 2003 6:00 AM
To: danny666@virgilio.it; www-rdf-logic@w3.org
Subject: Re: Presentation Syntax - why?


[Please note, this message is in reply to one from Danny Ayers that was
posted to public-webont-comments -- his message is included below -- I
have moved it here to avoid confusion with Last Call comment replies on
the public-comments list]

At 11:47 AM +0200 6/17/03, Danny Ayers wrote:
>At times it seems that the real activity of the WG can only be seen
like the
>structure of DNA was through X-Rays. A strange crystal that has just
>appeared on a plate is the OWL Web Ontology Language XML Presentation
Syntax
>Note [1]. There doesn't appear to be any documentation of the role of
>languages like this, and it's hard to place it in context.
>
>Reading the documentation for OWL it is clear that the intention was
for it
>to be a layer directly on top of RDF and RDFS, yet what the AS&S
describes
>needs a significant translation from OWL->RDF [2] and is currently only
>mappable in the RDF->OWL direction through quite a convoluted procedure
[3].
>
>The impression this gives is that AS&S has in large part been
constructed as
>an entirely new language, with the RDF(S) considerations being
retrofitted
>late in the day. How much truth there is in this isn't really
important,
>what is important is that the roadmap has become smudged.
>
>I believe significant clarification is required around certain issues,
in
>particular those that lead to the Presentation Syntax. It appears that
this
>is a concrete representation of the AS&S, but for what purpose? If the
>underlying model used by the AS&S is compatible with the RDF
graph/triples
>model, then why not use RDF/XML? Or is there such an air gap between
the RDF
>and OWL layers, that the OWL can fly free with it's own model, syntax
and
>serialization?
>
>On a practical level, the question is simple if a developer wishes to
build
>a Semantic Web application, where do they start? If they start with RDF
now,
>will they need a rework to be able to include OWL features without the
>struggle of [3]? Or if they start with OWL AS&S will they lose the
>compatibility with existing RDF data without building tools to carry
out the
>transformations of [2]?
>
>I realise this is relatively early days for OWL, it just seems from
what's
>being delivered that sometimes there are triples being asserted that
are
>dark for anyone outside of the WG.
>
>Cheers,
>Danny.
>
>[1] http://www.w3.org/TR/2003/NOTE-owl-xmlsyntax-20030611/
>
>[2]
http://www.w3.org/TR/2003/WD-owl-semantics-20030331/mapping.html#4.1
>
>[3] http://wonderweb.semanticweb.org/owl/parsing.shtml
>
>----
>
>http://dannyayers.com



Danny  - since this document isn't a Last Call document (and isn't
currently on the path to becoming one), I will take the liberty of
interacting without a Working Group mandate.  So these comments can be
considered my own opinion, not those of the group.
 Frankly, I don't understand your point of view as raised in this
message.  Most of the work I do in RDF is done using N3, because I find
it easier to use.  My tools translate that N3 to RDF/XML, which is then
used directly or turned into triples by some other tool.  WOuld you
argue against use of N3 or RDF/XML or Ntriples because they are all
variants on using "pure" RDF triples (as are stored into the underlying
RDF DB).
   OWL (Full) is a vocabulary extension to RDF (c.f [1] - my slides from
the W3C track at WWW).  It can be written directly in RDF/XML, it can be
written in N3, and now, thanks to the document you are complaining
about, there is an XML presentation that more directly corresponds to
the abstract syntax we use in proving the semantic properties of OWL
(and particularly the OWL DL profile of OWL).  This presentation syntax
comes with an XSLT that maps it into RDF/XML [2], and this is how we
would expect it to interact with other OWL (and RDF Core and RDFS)
tools. Thus,this syntax is just another way to produce OWL documents for
people who have a different tool set. 
   XML and RDF have different models, but many XML schemas can be mapped
into perfectly reasonable RDF/XML, and this is one of them.  It
guarantees  that documents that validate against this schema, and go
through this XSLT, end up as legal RDF documents consistent with the OWL
DL profile.  This is why we stress its role as a presentation syntax -
like N3 or Ntriples it is another way to look at RDF documents
  Other people are working on UML presentation syntax for OWL (the OMG
has released a call to produce a two-way mapping between UML-2 and OWL),
a graphical presentation syntax, a prolog front-end.  All of these
things lead to further adoption of OWL (and thus RDF) and I do not
understand why you think they could be bad things.

 I also must state that I am personally upset at your charge that the
activity of this working group is in any way mysterious.  Guus and Ihave
worked very hard as chairs, spurred on by Dan Connolly as team contact,
to make sure that everything the WG did was in public, and that every
decision we made was open to anyone who wanted to track it.  The issue
about whether to have an XML presentation has been in our publicly
available issues list since Oct 2002 [4].  The WG decided to have this
document as an "appendix" in Dec 02, but later decided a separate note
made more sense.   Further, our entire mail archive is open to the
public, and if you search on "XML presentation syntax" you will find
close to 150 messages dating back to May 2002 -- so you've had over a
year to "study the chrystalline structure of our DNA -- we've made it
damned easy to do!

  -Jim Hendler
p.s. I might also suggest you read the article Bijan Parsia and I wrote
in XML Journal [5], perhaps it can help clarify my position on why there
is no contradiction to having an XML presentation syntax for an RDF
vocabulary.
 


[1] http://www.w3.org/2003/Talks/0522-webont-hendler/
[2] http://www.w3.org/TR/2003/NOTE-owl-xmlsyntax-20030611/owlxml2rdf.xsl
[3]
http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.17-XML-presentati
on-syntax
[4]
http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.17-XML-presentati
on-syntax
[5]
http://www.mindswap.org/papers/XML-J-Oct2002.pdf




-- 
Professor James Hendler                           hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies         301-405-2696
Maryland Information and Network Dynamics Lab.      301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742      *** 240-277-3388 (Cell)
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