Standard WebDAV Properties

jamsden@us.ibm.com
Wed, 3 Mar 1999 16:50:34 -0500


From: jamsden@us.ibm.com
To: w3c-dist-auth@w3.org, ietf-dav-versioning@w3.org
Message-ID: <85256729.0078BA14.00@d54mta03.raleigh.ibm.com>
Date: Wed, 3 Mar 1999 16:50:34 -0500
Subject: Standard WebDAV Properties



The WebDAV protocol supports a number of functions including collections,
properties, namespace management, and soon to come, ordered collections,
references, versioning, parallel development, configuration management, and
searching. However, in spite of all these functions, client applications
often want more. For example, a typical document management application
might do document life cycle management functions like review and approval
cycles, document states and transitions, rendering variants in multiple
document formats, workflow and groupware functions, notification,
publishing, etc. These client applications can exploit new resource types
and WebDAV properties to implement these functions, but unless multiple
client applications implement them the same way, interoperability is
compromised. We could extend WebDAV to include all these capabilities, but
then the protocol would get very complex, take a long time to develop, and
include too many domain specific concepts what would not be reused for
other domains. So how do we support new functions, promote
interoperability, and keep the protocol domain neutral and simple?

One approach is to take a lesson from XML. XML is a standard language for
tagged documents. The standard specifies (among other things) that an XML
document contains elements which have attributes and can contain other
elements. So XML, unlike HTML, defines a standard syntax for documents, but
not a standard for their specific content structure. A class of documents
can be described using a Document Type Definition (DTD) that specifies the
valid element structure for that class of documents.  A DTD defines a
"document language" that can be used to describe and validate documents
that conform to that language. Interested industries can get together and
define a document language for their industry. Then applications
interoperate at two levels: one using XML documents as a common interchange
format, and another using agreed upon DTDs to describe the structure of
these documents. XML doesn't have to change to support Health Care or the
Automotive Industry, those industries just have to agree on their
respective DTDs. There are standards efforts underway to facilitate the
construction of these DTDs. For example:

  - CDF  for push applications
  - CIM2  for systems and network management apps
  - EAD  for apps which need access to archival inventories and registers
  - HTML4  for Web documents
  - MathML for mathematics
  - OAG  for supply chain applications
  - OTP  for eCommerce applications
  - PGML  for graphics
  - RosettaNet  their catalog DTD for use in eCommerce
  - SMIL  for streaming media apps
  - vCard  for applications needing to process an electronic business card
  - WML - for transcoding applications to wireless PvC devices
  - iCal  - for calendar and calendar-related events

There are also web sites that provide a repository for DTDs so that
interested parties can see what other people are doing in the same domain,
and can locate potential collaborators. See http://www.schema.net.

We could do something similar for client extensions to WebDAV based on
resource types and properties. This could be facilitated by establishing a
web site that WebDAV client developers could visit and contribute to that
would contain proposals for properties and resource document types to
support particular domains. For example, one could envision a consortium of
document management providers who would collaborate on resource types and
properties to support document life cycle management as described above.
This would allow client providers to establish standards without extending
the WebDAV protocol for particular domains of interest while still enabling
interoperability. Client applications could continue to add value of their
own, but could expect that documents conforming to the standard would have
expected properties and structure.

I propose that we establish such a web site, and that the WebDAV working
groups may want to exploit this concept themselves instead of adding a lot
of DAV properties to the standard that may prove to be too domain specific
for general reuse, or result in too may server options for clients to be
effectively written.