Counting extensional differences in BC-learning

  • Authors:
  • Sanjay Jain;Frank Stephan;Sebastiaan A. Terwijn

  • Affiliations:
  • School of Computing, National University of Singapore, Singapore 117543, Singapore;Mathematisches Institut, Universität Heidelberg, Im Neuenheimer Feld 294, 69120 Heidelberg, Germany;Institute for Algebra and Computational Mathematics, Technical University of Vienna, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria

  • Venue:
  • Information and Computation
  • Year:
  • 2004

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Abstract

Let BC be the model of behaviourally correct function learning as introduced by Bärzdins [Theory of Algorithms and Programs, vol. 1, Latvian State University, 1974, p. 82-88] and Case and Smith [Theoret. Comput. Sci. 25 (1983) 193-220]. We introduce a mind change hierarchy for BC, counting the number of extensional differences in the hypotheses of a learner. We compare the resulting models BCn to models from the literature and discuss confidence, team learning, and finitely defective hypotheses. Among other things, we prove that there is a trade-off between the number of semantic mind changes and the number of anomalies in the hypotheses. We also discuss consequences for language learning. In particular we show that, in contrast to the case of function learning, the family of classes that are confidently BC-learnable from text is not closed under finite unions.