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RE: Presentation Syntax - why?

From: Bradley P. Allen <ballen@siderean.com>
Date: Tue, 17 Jun 2003 11:01:59 -0700
To: "'Jim Hendler'" <hendler@cs.umd.edu>, <danny666@virgilio.it>, <www-rdf-logic@w3.org>
Message-ID: <002101c334fa$8d30f490$6401a8c0@FISHBOWL>
I have two problems. The first is the effort to absorb yet another
Semantic Web dialect in my application, and the second is the effort to
explain the reasons for yet another dialect to a user community. The
first is a short-term cost I have to bear. I fear the second can hinder
adoption of the technology.
As to the first: you're right. We shouldn't care, as we do routinely
apply stylesheets to transform arbitrary XML into RDF/XML. It is a good
thing that the Note contains a draft stylesheet in an appendix. But it's
an interoperability issue because it's one more mapping that I will now
have to worry about. However minimal that might be in this case, the
working assumption was that all OWL in XML that we would encounter would
be RDF/XML with OWL vocabulary. I am now disabused of that notion, and
having complained, I will deal with it.
With respect to the second: I assume, based on what you say, that some
in the Webont WG feel that making it easier to write OWL DL correctly is
worth abandoning RDF/XML as an authoring language. While I can
appreciate their reasons, I think you are discounting the amount of FUD
this creates among developers who are just beginning to understand what
can be accomplished by authoring RDF/XML as it is today. I think it's
worth addressing more explicitly in the Note and elsewhere, as you have
in your email.
- regards, BPA
Bradley P. Allen
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: Jim Hendler [mailto:hendler@cs.umd.edu] 
Sent: Tuesday, June 17, 2003 7:43 AM
To: ballen@siderean.com; danny666@virgilio.it; www-rdf-logic@w3.org
Subject: RE: Presentation Syntax - why?

At 7:24 AM -0700 6/17/03, Bradley P. Allen wrote:
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
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
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

Brad - this is what I don't understand.  Why is the presentation syntax
"another interoperability issue to address"??  Anyone using it will have
to run the stylesheet and turn it into rdf/xml if they want any tools to
do anything useful with it -- the reasoners, etc. will all use the RDF.
So any tools you build will simply be enhanced by having more ontologies
around in RDF/XML (or someone will build a crawler to find the XML ones
and map to RDF or etc.) -- the implementor of an OWL or RDF tool
shouldn't be effected by this at all.  The reason some in the Webont WG
like this, is because any document that validates against this XML
schema will map to a legal OWL DL graph -- those are hard to check, and
thus this will increase the number of people creating legal OWL DL
ontologies.  Those of us working in RDF will use OWL Full in most cases,
which means we don't need to worry about the well-formedness conditions
of the DL profile, but all OWL DL graphs are OWL Full graphs, so we'll
be able to use our tools on them as well - win, win.
 so frankly, I see anything that causes more RDF to exist to be
beneficial, and don't understand why "throwing a stylesheet over the
wall just doesn't cut it", this is the WEB damn it, we win if more
documents in more formats become interoperable -- not by saying everyone
must do things in one particular way
 I know there are some good documents about "loose coupling" that have
been chumped in the rdfig chat -- I'm a firm devotee of the loose
coupling philosophy (and designed the entire DARPA DAML initiative to
promote it) - and thus I don't see where the problem comes in -- what do
you care what tool I use to create my graphs as longs as you can process


-----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
>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
>needs a significant translation from OWL->RDF [2] and is currently only
>mappable in the RDF->OWL direction through quite a convoluted procedure
>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
>late in the day. How much truth there is in this isn't really
>what is important is that the roadmap has become smudged.
>I believe significant clarification is required around certain issues,
>particular those that lead to the Presentation Syntax. It appears that
>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
>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
>On a practical level, the question is simple if a developer wishes to
>a Semantic Web application, where do they start? If they start with RDF
>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
>being delivered that sometimes there are triples being asserted that
>dark for anyone outside of the WG.
>[1] http://www.w3.org/TR/2003/NOTE-owl-xmlsyntax-20030611/
>[3] http://wonderweb.semanticweb.org/owl/parsing.shtml

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
   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

[1] http://www.w3.org/2003/Talks/0522-webont-hendler/
[2] http://www.w3.org/TR/2003/NOTE-owl-xmlsyntax-20030611/owlxml2rdf.xsl

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)
http://www.cs.umd.edu/users/hendler      *** NOTE CHANGED CELL NUMBER

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)
http://www.cs.umd.edu/users/hendler      *** NOTE CHANGED CELL NUMBER
Received on Tuesday, 17 June 2003 14:02:32 UTC

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