Multimedia Tools and Applications

, Volume 50, Issue 3, pp 465–489 | Cite as

Variable and state handling in NCL

  • Luiz Fernando G. Soares
  • Rogério Ferreira Rodrigues
  • Renato Cerqueira
  • Simone Diniz Junqueira Barbosa
Article

Abstract

Most time-based declarative languages have limited support for variable definition and manipulation, which causes developers to resort to imperative languages. However, a declarative language should provide a variable handling model sufficiently rich to describe a wide range of interactive applications, avoiding, as much as possible, the help of an imperative scripting language. On the other hand, the declarative simplicity should not be lost, leaving for the imperative objects more complex manipulations, with the necessary care to avoid any impact in the application’s temporal graph. Based on this principle, variables and the presentation state are handled by NCL and Ginga-NCL, as discussed in this paper. NCL is the declarative language of the Brazilian Terrestrial Digital TV System (SBTVD) supported by its middleware called Ginga. NCL and Ginga-NCL are part of ISDB standards and also of ITU-T Recommendations for IPTV services.

Keywords

Variable handling Declarative languages NCL Digital TV Middleware 

Notes

Acknowledgments

The authors would like to thank Carlos Salles, Romualdo Costa, Marcio Moreno, Marcelo Moreno and Francisco Sant’anna who provided thoughtful discussion of this work, and tracked down and fixed problems in the initial reference implementation of Ginga. The authors also thank Ethan Munson for his careful revision of the paper, and CNPq, FINEP and FAPERJ for their support.

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Luiz Fernando G. Soares
    • 1
  • Rogério Ferreira Rodrigues
    • 1
    • 2
  • Renato Cerqueira
    • 1
  • Simone Diniz Junqueira Barbosa
    • 1
  1. 1.Pontifícia Universidade Católica do Rio de JaneiroRio de JaneiroBrazil
  2. 2.Microsoft® Corporation/FAST, a Microsoft® SubsidiaryRio de JaneiroBrazil

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