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RE: DAV Schema Assessment (was Re: rfc2518bis DAV DTD ...)

From: Eric Sedlar <eric.sedlar@oracle.com>
Date: Fri, 17 Oct 2003 09:52:30 -0700
Message-Id: <200310171652.h9HGqhK19052@rgmgw4.us.oracle.com>
To: "'Julian Reschke'" <julian.reschke@gmx.de>, <w3c-dist-auth@w3.org>

There are two possible use cases for a schema language to describe DAV XML
syntax.  Case 1 is as a tool like BNF to formally describe the protocol.  A
second is in the case where people would actually do validation at runtime.
I don't think that most WebDAV implementations today actually run DTD
validation.  For use case 1, XML Schema is fine since there is no backwards
compatibility issue.  If you want to require use case 2, then people would
have to include a validation engine in their WebDAV implementations.  If
WebDAV WG chose RELAX NG for use case 2, then all WebDAV vendors would have
to acquire or develop RELAX implementations, which to me, is pushing RELAX
on people.  If all we care about is case 1, we could always write our
standards using XML Schema, but just note that the schemas are for a formal
description rather than for use in implementations.

As far as your name-calling, goes, yes, Relax is almost a real ISO standard
like X.400 and other such successes from the ISO.  They're much better than
those poorly specified ones coming from IETF and W3C like SMTP and HTTP.  I
don't know why we have to descend into bashing of particular vendors or
standards organizations to have this discussion.  W3C is the organization
that currently owns most of the related standards we deal with in WebDAV,
such as XML and HTTP, so yes, I believe its standards are more relevant than
ISO ones when a conflict occurs (also note the mail address of this list).
Schema was designed by a large committee to meet the needs of a wide variety
of organizations and applications (e.g. structure definition, not just
validation), as opposed to RELAX, which was designed by one guy.  That's why
Schema has more market acceptance and RELAX is more elegant.  In general,
the IETF and the WebDAV WG has tried to keep discussions rooted in
practicality--what's actually out there in the bulk of the users.  As far as
what major vendors are doing, since you mentioned my employer, I would point
out that your employer is also a proponent of XML Schema (quoted from
http://www.w3.org/2001/05/xml-schema-testimonial.html):

SAP is pleased to see that XML Schema has become a W3C Recommendation. XML
Schema is a key integration technology for supporting tightly coupled
business processes through loosely coupled components within and outside of
the company boundary and an essential standard for building and leveraging
shared knowledge about collaborative services and processes. SAP is
committed to embracing XML Schema throughout the mySAP.com e-business
platform by providing XML-based services and leveraging XML Schema to
support business integration within mySAP Technology.
-- Dr. Peter Barth, Director Corporate Marketing mySAP Technology and mySAP
Workplace, SAP AG

--Eric

> -----Original Message-----
> From: w3c-dist-auth-request@w3.org [mailto:w3c-dist-auth-request@w3.org]
> On Behalf Of Julian Reschke
> Sent: Friday, October 17, 2003 12:20 AM
> To: Eric Sedlar; Julian Reschke; w3c-dist-auth@w3.org
> 
> 
> Eric,
> 
> > There's not much interest in Relax NG in actual vendor products.  Unless
> > people are actually going to use validators, I don't think we should
> push
> > Relax NG on people.
> 
> I think that's a non-issue. We don't want to push *any* particular
> language
> on people. We were looking for something that would work better than DTDs,
> and RelaxNG seems to do that (it can express what we want and it has a
> readable syntax suitable for embedding in specs).
> 
> If the requirement for the notation actually is that it needs to be a W3C
> spec and there have to be implementations by Microft, IBM and Oracle, then
> we can stop this discussion right away. The only alternative to DTDs would
> be XML Schema, and we know that it doesn't work. In which case we should
> go
> back to the original question about what we want to say normatively about
> the DTD fragments we use.
> 
> On the other hand, RelaxNG fulfills all technical requirements, has
> working
> open source reference implementations, is as open as a spec as XML Schema
> (although Oasis instead of W3C) *and* is on it's way to a real ISO
> standard
> (something you can't say about XML Schema).
> 
> Julian
> 
> --
> <green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760
> 
> > -----Original Message-----
> > From: w3c-dist-auth-request@w3.org
> > [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Eric Sedlar
> > Sent: Friday, October 17, 2003 12:39 AM
> > To: Julian Reschke; dennis.hamilton@acm.org; Stanley Guan;
> > w3c-dist-auth@w3.org
> > Subject: Re: DAV Schema Assessment (was Re: rfc2518bis DAV DTD ...)
> >
> >
> >
> 
> >
> > --Eric
> >
> > ----- Original Message -----
> > From: "Julian Reschke" <julian.reschke@gmx.de>
> > To: "Julian Reschke" <julian.reschke@gmx.de>; <dennis.hamilton@acm.org>;
> > "Stanley Guan" <stanley.guan@oracle.com>; <w3c-dist-auth@w3.org>
> > Sent: Thursday, October 16, 2003 2:50 PM
> > Subject: RE: DAV Schema Assessment (was Re: rfc2518bis DAV DTD ...)
> >
> >
> > >
> > > OK,
> > >
> > > I just spend a few minutes with Jing (Relax NG validator) and Trang
> > (Schema
> > > Language convertor) [1]. Some initial thoughts:
> > >
> > > - RelaxNG can express WebDAV's extensibility model
> > > - RelaxNG has both an XML based syntax ( la XML Schema) and a Compact
> > > syntax ( la DTD)
> > > - Trang supports to/from DTD, XML Schema, RelaxG (compact/XML) and (!)
> > > sample XML instance data
> > > - RelaxNG supports the XML schema datatypes
> > >
> > > Here's an example for dav:propfind in RNC (Relax NG Compact Syntax):
> > >
> > > namespace dav = "DAV:"
> > >
> > > start = propfind
> > >
> > > allprop = element dav:allprop { empty }
> > >
> > > prop =
> > >   element dav:prop {
> > >     element * { empty }+
> > >   }
> > > propname = element dav:propname { empty }
> > > propfind = element dav:propfind { (allprop | prop | propname) & EXT? }
> > >
> > > EXT =
> > >   element * - (dav:allprop
> > >                | dav:href
> > >                | dav:multistatus
> > >                | dav:prop
> > >                | dav:propfind
> > >                | dav:propname
> > >                | dav:response
> > >                | dav:status) { empty }
> > >
> > > ...you get the idea.
> > >
> > > Should we pursue this?
> > >
> > > Julian
> > >
> > >
> > > [1] <http://www.relaxng.org/>
> > >
> > > --
> > > <green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760
> > >
> > >
> > >
> >
Received on Friday, 17 October 2003 12:52:50 GMT

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