Why Horn formulas matter in computer science: initial structures and generic examples
Journal of Computer and System Sciences
A logic for partially specified data structures
POPL '87 Proceedings of the 14th ACM SIGACT-SIGPLAN symposium on Principles of programming languages
An interpretation of negation in feature structure descriptions
Computational Linguistics
What You Always Wanted to Know About Datalog (And Never Dared to Ask)
IEEE Transactions on Knowledge and Data Engineering
CLG: A Grammar Formalism Based on Constraint Reslution
EPIA 89 Proceedings of the 4th Portuguese Conference on Artificial Intelligence
A unification method for disjunctive feature descriptions
ACL '87 Proceedings of the 25th annual meeting on Association for Computational Linguistics
Conditional descriptions in Functional Unification Grammar
ACL '88 Proceedings of the 26th annual meeting on Association for Computational Linguistics
Unification of disjunctive feature descriptions
ACL '88 Proceedings of the 26th annual meeting on Association for Computational Linguistics
Computing with features as formulae
Computational Linguistics
Deterministic consistency checking of LP constraints
EACL '95 Proceedings of the seventh conference on European chapter of the Association for Computational Linguistics
Logical investigations on the adequacy of certain feature-based theories of natural language
NAACL-DocConsortium '06 Proceedings of the 2006 Conference of the North American Chapter of the Association for Computational Linguistics on Human Language Technology: companion volume: doctoral consortium
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The notion of a Horn extended feature structure (HoXF) is introduced, which is a feature structure constrained so that its only allowable extensions are those satisfying some set of Horn clauses in feature-term logic. HoXF's greatly generalize ordinary feature structures in admitting explicit representation of negative and implicational constraints. In contradistinction to the general case in which arbitrary logical constraints are allowed (for which the best known algorithms are exponential), there is a highly tractable algorithm for the unification of HoXF's.