Lessons from Some Real-Time Hypermedia Systems

John Buford
Distributed Multimedia Systems Lab
Dept of Computer Science
University of Massachusetts Lowell
http://dmsl.cs.uml.edu/~buford

Since 1991 the Distributed Multimedia System Lab has been developing
real-time multimedia and hypermedia systems [1]. The HyOctane (TM) 
hypermedia engine is the first published system to deploy a HyTime
application [2]. We wrote the first Java applet to present a HyTime
application in 1995.  We also participated in the design of and developed
one of the first prototypes of an MHEG system [3]. Recently we have
completed a Java application that parses and presents MHEG-5
objects retrieved using MPEG DSM-CC interface which is also written
in Java.   The international interactive TV consortium, DAVIC,
has adopted MHEG-5 and the Java VM; the MHEG-6 CD, which has just
been released, defines the integration of the Java VM and MHEG-5.

The activities of MHEG, HyTime and more recently the DAVIC 
interactive TV consortium have been overlooked by many of the 
web community.  This workshop is an appropriate venue for the
architects of the web's multimedia evolution to review both
the positive and negative features of predecessor standards.
The current situation is somewhat similar to the recent emergence
of distributed object systems in the web architecture [4]; 
e.g., Netscape has announced that they expect the OMG IIOP
to ultimately replace http.  With regard to real-time multimedia,
the lack of a standard multimedia framework and architecture 
in the web will likely lead to a variety of proprietary and 
incompatible approaches unless appropriate standards are adopted.

The issues are both technical and market-based.  On the technical
side, the issues of supporting continuous media (CM) applications
in distributed systems have been studied for some time.  It is
generally agreed that real-time CM applications require resource
management which includes concepts of QOS, resource reservation,
orchestration, scheduling, and recovery.  Much less has been
done to address CM in hypermedia applications, but see [5].
Standards such as RTP and RSVP will be part of the solution.

On the market front, content is the key to success in interactive
television applications, and content providers are interested in
access to large markets that are not fragmented by different 
delivery mechanisms and formats.  In the DAVIC model this has
been addressed by specifying a base required format that every
set-top should support (i.e., MHEG-5) and allowing any third-party
player to be downloaded, which may provide custom functionality.

This presentation will discuss the lessons from HyTime and MHEG
and compare different alternatives for the web to provide
document model support for real-time multimedia applications.

References

1. J. Buford, contr. ed., Multimedia Systems.  ACM Press. 1994. 

2. J. Buford, L. Rutledge, C. Keskin, and J. Rutledge. HyOctane: A HyTime Engine for an MMIS. J. Multimedia Systems (1) 4, 1994.

3. J. Buford, and C. Gopal, Standardizing a Multimedia Interchange Format: A Comparison of OMFI and MHEG. 1994 IEEE Intl Conf on Multimedia Computing and Systems, May 1994.

4. J. Buford. CORBA and WWW: On a Collision Course. Joint W3C/OMG Workshop on Distributed Objects and Mobile Code. Boston, June 1996. 

5. J. Buford and L. Rutledge. Third Generation Distributed Hypermedia Systems. in Handbook of Multimedia Information Management (ed. W. Grosky, R. Jain, and R. Mehrotra), Prentice Hall. 

6. C. Gopal and J. Buford. Delivering Hypermedia Sessions from a Continuous Media Server. in Multimedia Information Storage and Management (ed. S. Chung). Kluwer Press. 

7. L. Rutledge, J. Buford, R. Price. Mobile Objects in the Distributed HyOctane Hyperdocument Server. Proc. IMC 96. Rostock, Germany, Feb. 1996.

8. J. Buford. Distributed Multimedia Information Systems. SPIE Critical Reviews (ed. M. Nier). Feb 1996.

9. J. Buford. HyTime: Evaluation and Implementation Experience. Proc. ACM Hypertext 96, March 1996. Washington DC

10. J. Buford. Evaluation of a Query Language for Structured Hypermedia Documents. Proc. DAGS 95--Electronic Publishing and the Information Superhighway. May 1995