Papers in PDF format

to be combined; this integration activity is termed MHEG-6. A DAVIC 1.0 interoperability trial has been
successfully conducted in June 1996 [Columbia 96].
ITV systems will use a low-cost Set Top Box (STB) [Furht et al. 95] that can be configured remotely to
connect to the outside world. They will also use new high bandwidth network architectures like ATM,
HFC, and ADSL to provide the necessary higher bandwidth to the consumer. Most ITV applications will
be downloaded incrementally because of memory limitations. It seems likely that in the future many
consumers will have access to high-bandwidth information services through an ITV provider such as a
cable TV or telephone service. Consequently, the ITV standards developed by DAVIC are likely to be
important for developing web client and server standards which support real-time video and audio
delivery. Similarly, MHEG-5, which provides both a time-composition model and an object-oriented
framework for incremental delivery of content, may also be relevant to future extensions to HTML, which
currently lacks these key features.
The purpose of this paper is to briefly review the DAVIC model and MHEG-5 with the expectation that
there will be a future relationship between deployed ITV systems and Internet and web systems. Table 1
compares features of the WWW and DAVIC.
2. Overview of MHEG-5
Features WWW DAVIC
Document Encoding HTML MHEG-5 required, other formats optional
Real-time delivery No Yes
Stream interface None DSM-CC Stream functionality
Session Management None DSM-CC (U-N protocols)
Inter Media Synchronization None Through MHEG-5 links
Table 1: Features of WWW and DAVIC
MHEG-5 [MHEG 95] belongs to the suite of standards known as MHEG [Buford 94]. It defines the
semantics and final form for interchangeable objects intended for composition of simple interactive
multimedia applications in a client/server architecture, ensuring the interoperability across heterogeneous
platforms. MHEG-5 like its predecessor MHEG-1, is intended for low-end delivery systems. MHEG-5 has
a more precise conformance requirement than MHEG-1, and is generally considered to have a clearer and
less complex design.
Multimedia applications in the context of MHEG-5 are event-driven. They are composed of a web of
scenes and link objects which define navigating between scenes and the actions that must be executed
when some specified events occur. Most of the applications can be developed using only declarative code,
although MHEG-5 provides means to perform tasks which are better expressed in a procedural paradigm.
A scene object groups visual, audible, interaction, and link objects. Consequently, the application and all
its scenes with related objects, are designed only once and delivered using MHEG-5 object Servers. The
objects are downloaded to the client and the MHEG-5 run-time engine is responsible for decoding,
interpreting, presenting, and managing them.