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Source-Tracking Unification

  • Venkatesh Choppella
  • Christopher T. Haynes
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2741)

Abstract

We propose a practical path-based framework for deriving and simplifying source-tracking information for term unification in the empty theory. Such a framework is useful for debugging unification-based systems, including the diagnosis of ill-typed programs and the generation of success and failure proofs in logic programming.

The objects of source-tracking are deductions in the logic of unification. The semantics of deductions are paths over a unification graph whose labels form the language of suffixes of a semi-Dyck set. Based on this framework, two algorithms for generating proofs are presented: the first uses context-free shortest-path algorithms to generate optimal (shortest) proofs in time O(n 3), where n is the number of vertices of the unification graph. The second algorithm integrates easily with standard unification algorithms, entailing an overhead of only a constant factor, but generates non-optimal proofs. These non-optimal proofs may be further simplified by group rewrite rules.

Keywords

Normal Form Logic Program Logic Programming Type Inference Term Equation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • Venkatesh Choppella
    • 1
  • Christopher T. Haynes
    • 1
  1. 1.Computer Science DepartmentIndiana UniversityBloomingtonUSA

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