Position Paper:  Joint W3C/OMG Workshop on Distributed Objects and Mobile Code

Bill Janssen, Xerox PARC  (janssen@parc.xerox.com)

The ILU project at PARC is an outgrowth of earlier research into
distributed document systems, in particular the notions behind
construction of universal browsers that could examine any document
space, regardless of document type.  It became clear that in order to
do this, a clear language-independent notion of object types would be
needed, supported by an underlying technology of distributed objects.
We feel that this need is also present in the current notion of the
World Wide Web, and that the notion of object types present in ILU,
and the distributed object systems embodied in CORBA orbs, are
reasonable responses to these needs.

ILU (ftp://ftp.parc.xerox.com/pub/ilu/ilu.html) is a multi-language
object interface system.  The object interfaces provided by ILU hide
implementation distinctions between different languages, between
different address spaces, and between operating system types.  ILU can
be used to build multi-lingual object-oriented libraries ("class
libraries") with well-specified language-independent interfaces.  It
can also be used as a distributed object system.  ILU interfaces are
specified in ILU's Interface Specification Language.  ISL is not quite
OMG IDL, as it provides several extensions to OMG IDL which we feel
are crucial to providing effective implementations of things like the
World Wide Web on top of a distributed object system.

We see a number of opportunities for a CORBA-like object system to
play an important role in the World Wide Web.  Links between Web
servers and specific services can be made faster and more flexible by
replacing the current CGI API with a method invocation on an ILU
object, as Digital Creations' ILU Requester has done
(http://www.digicool.com/releases/ilurequester/).  Browsers can export
ILU interfaces to allow manipulation by other applications in the
user's space.  Proxy servers and cache servers can coordinate their
databases using ILU-based protocols similar to those described by the
Bayou project (http://www.parc.xerox.com/csl/projects/bayou/).

Perhaps most interestingly, current Web usage could be radically
improved by augmenting the current HTTP protocol with a carefully
designed set of object types, and an optimized wire protocol for
conveying method invocations and responses.  We are currently
participating in an experiment by the World Wide Web Consortium to
devise such a set of types, and such a wire protocol
(http://www.w3.org/pub/WWW/Protocols/HTTP-NG/Overview.html).  This
experiment, if successful, provides the opportunity to greatly expand
the numbers and kinds of objects accessible via the Web, as well as
changing our notions of what a ``document'' is.  Some of these notions
are already being explored by the Digital Library research
initiatives, several of which have chosen to use ILU to tie together
their systems.  We hope to bring some of the ideas realized in this
research to the Web, as well.