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RE: Presentation Syntax - why?

From: Jim Hendler <hendler@cs.umd.edu>
Date: Tue, 17 Jun 2003 14:25:37 -0400
Message-Id: <p05200f39bb150bcc1adb@[]>
To: <ballen@siderean.com>, <danny666@virgilio.it>, <www-rdf-logic@w3.org>
At 11:01 AM -0700 6/17/03, Bradley P. Allen wrote:

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.

I understand the reservation, but some argue this will augment, 
rather than hinder, the adoption.  My feeling has always been that 
the Web is big enough that we should build as many usable things as 
we can, and that only conflicting standards are likely to hinder 
adoption -- in this case, all the syntaxes play well together, so I 
don't see that problem

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 

I still don't understand this at all.  The only OWL in XML you will 
ever encounter is indeed RDF/XML with OWL vocabulary.  The stuff in 
the presentation syntax would be mapped to that before it would be 
expected to be used - otherwise it violates the assumptions of OWL 
(i.e. that RDF/XML is the exchange language for OWL documents) - 
nothing in this note changes that.

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

It's not ABANDONING - look, think of this as a macro package for 
programming in OWL.  It expands to exactly the same stuff - but if 
you use these macros you know your program will generate one of the 
many legal graphs that could express the same content, and that the 
graph will be consistent with a set of rules you would have to deal 
with by hand without such a thing (or some other tool).  One of the 
reasons we released the presentation syntax was complaints from 
people that the OWL S&AS was too difficult to use and to map into RDF 
graphs -- okay, just consider this to be an operationalization of 
that mapping  I think it might actually be useful in some small 
number of cases :->)

I just don't see a downside.  Here, think of it this way - if you 
build an OWL tool, you can sell or advertise an extension to produce 
XML documents that correspond to the ontologies (and thus can be 
saved, sorted, searched, etc. using XML tools) - you make extra 
money, and we've done all the work :->

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 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
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 them??

-----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
>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.
>[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

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 
   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

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 ***

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 14:25:49 UTC

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