Characterization Results for Time-Varying Codes

  • Authors:

  • Ferucio Ţiplea;Erkki Mäkinen;Dragos Trincă;Costel Enea

  • Affiliations:

  • Faculty of Computer Science, ``Al.I.Cuza'' University of Iaşi, 6600 Iaşi, Romania;Department of Computer and Information Sciences, P.O. Box 607, FIN-33014 University of Tampere, Finland;Faculty of Computer Science, ``Al.I.Cuza'' University of Iaşi, 6600 Iaşi, Romania;Faculty of Computer Science, ``Al.I.Cuza'' University of Iaşi, 6600 Iaşi, Romania

  • Venue:
  • Fundamenta Informaticae
  • Year:
  • 2002

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Abstract

Time-varying codes associate variable length code words to letters being encoded depending on their positions in the input string. These codes have been introduced in [8] as a proper extension of L codes. This paper is devoted to a further study of time-varying codes. First, we show that adaptive Huffman encodings are special cases of encodings by time-varying codes. Then, we focus on three kinds of characterization results: characterization results based on decompositions over families of sets of words, a Schützenberger like criterion, and a Sardinas-Patterson like characterization theorem. All of them extend the corresponding characterization results known for classical variable length codes.