Mode-Directed Tabling and Applications in the YapTab System

João Santos and Ricardo Rocha

June 2012

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Abstract

Tabling is an implementation technique that solves some limitations of Prolog's operational semantics in dealing with recursion and redundant sub-computations. Tabling works by memorizing generated answers and then by reusing them on similar calls that appear during the resolution process. In a traditional tabling system, all the arguments of a tabled subgoal call are considered when storing answers into the table space. Traditional tabling systems are thus very good for problems that require finding all answers. Mode-directed tabling is an extension to the tabling technique that supports the definition of selective criteria for specifying how answers are inserted into the table space. Implementations of mode-directed tabling are already available in systems like ALS-Prolog, B-Prolog and XSB. In this paper, we propose a more general approach to the declaration and use of mode-directed tabling, implemented on top of the YapTab tabling system, and we show applications of our approach to problems involving Justification, Preferences and Answer Subsumption.

Bibtex

@InProceedings{santos-slate12,
  author =    {J. Santos and R. Rocha},
  title =     {{Mode-Directed Tabling and Applications in the YapTab System}},
  booktitle = {Proceedings of the Symposium on Languages, Applications and Technologies (SLATE 2012)},
  pages =     {25--40},
  editor =    {A. Simões and R. Queirós and  D. Cruz},
  month =     {June},
  year =      {2012},
  address =   {Braga, Portugal},
}

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