Requirements from PUC-Rio and ITU-T for Web+TV
MORENO, Marcelo (ITU-T)
SOARES, Luiz Fernando (TeleMidia Lab - PUC-Rio)
KAWAMORI, Masahito (ITU-T)

TeleMidia Lab is a research group of the Informatics Department at  Pontifical Catholic University of Rio de Janeiro (PUC-Rio). TeleMidia R&D activities are concentrated in two major areas: Multimedia Data Communication and Multimedia/Hypermedia Systems. A remarkable recent result of PUC-Rio work is Ginga-NCL, the declarative middleware for ISDB-Tb terrestrial DTV system and a Multimedia Application Framework for IPTV services in ITU-T.

Over the last several years ITU-T has adopted a leadership role in promoting collaborative work on developing global standards for IPTV, first in the IPTV Focus Group activities and subsequently in the IPTV-GSI. These initiatives have been very successful in bringing together the IPTV related work going on in a number of standardization organizations such as ATIS IIF, ETSI TISPAN, DVB Project, to develop a set of global standards on various aspects of IPTV.

PUC-Rio and ITU-T would like to share with W3C some of the requirements we pursued during the development and standardization of Ginga-NCL and the IPTV Multimedia Application Framework. We think the requirements briefly described below should also be considered on the specification of technologies that integrate Web and TV.

- Lightweight user agent. Web+TV applications should run on resource-limited devices like TV sets, mobile phones and portable TVs.

- Intermedia synchronization. Web+TV applications are rich multimedia presentations that relates many media objects in time and space. Web+TV technologies should support intermedia spatiotemporal synchronization.

- Content personalization/adaptation. Web+TV applications may take user preferences and device characteristics into account to provide viewers the best experience.

- Live content. Web+TV applications may be related to live-generated content, so the modification of their behavior at runtime should be possible.

- Multidevice presentation. Content producers don't like to see their masterpieces polluted with Web information. Moreover, viewer interactions usually annoy other viewers seeing the same program at the same place. Applications may also demand collaborative interactive actions among viewers. The solution to these problems may be the use of multiple devices working in cooperation in the exhibition of Web+TV applications. 

- Easy programming. Web+TV applications are created by Web designers and audiovisual producers. Languages and tools for Web+TV applications should be easy and powerful. 

- Harmonization. Web+TV technologies should provide the harmonization of  media types and development languages commonly used in the Web, TV, and portable computing domains.

NCL (Nested Context Language) was designed to address the requirements listed in this paper. NCL is an XML-based glue language, which does not prescribe or restrict any type of media objects. An NCL application just specifies the spatiotemporal relationships among media objects. Therefore, NCL is able to embed any type of media objects, just depending on which media players are embedded into the Ginga-NCL implementation. For instance, we can have HTML-based objects embedded into NCL applications, since an HTML player (Web browser) can be embedded into Ginga-NCL.

Currently, PUC-Rio is working on future versions of NCL to introduce support for 3D interactive content, to improve content adaptation and multidevice presentation support, to provide better support for social TV applications and to specify lower-level representations for NCL, aiming at more efficient user agents and transport systems.