An algebraic semantics approach to the effective resolution of type equations
Theoretical Computer Science
Why Horn formulas matter in computer science: initial structures and generic examples
Journal of Computer and System Sciences
Efficient implementation of lattice operations
ACM Transactions on Programming Languages and Systems (TOPLAS)
The logic of typed feature structures
The logic of typed feature structures
Inheritance, defaults and the lexicon
Inheritance, defaults and the lexicon
Types and constraints in the LKB
Inheritance, defaults and the lexicon
Approximation algorithms for NP-hard problems
Approximation algorithms for NP-hard problems
COLING '94 Proceedings of the 15th conference on Computational linguistics - Volume 2
Feature logic with disjunctive unification
COLING '90 Proceedings of the 13th conference on Computational linguistics - Volume 2
Computer Algorithms
Domain-independent extensions to GSAT: solving large structured satisfiability problems
IJCAI'93 Proceedings of the 13th international joint conference on Artifical intelligence - Volume 1
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One may identify two main approaches to the description of type hierarchies. In total specification, a unique hierarchy is described. In open specification, a set of constraints identifies properties of the hierarchy, without providing a complete description. Open specification provides increased expressive power, but at the expense of considerable computational complexity, with essential tasks being NP-complete or NP-hard. In this work, a formal study of the structural and computational aspects of open specification is conducted, so that a better understanding of how techniques may be developed to address these complexities. In addition, a technique is presented, based upon Horn clauses, which allows one to obtain answers to certain types of queries on open specifications very efficiently.