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Ordering Constraints over Feature Trees
, 1999
"... Feature trees are the formal basis for algorithms manipulating record like structures in constraint programming, computational linguistics and in concrete applications like software configuration management. Feature trees model records, and constraints over feature trees yield extensible and modular ..."
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Cited by 12 (5 self)
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Feature trees are the formal basis for algorithms manipulating record like structures in constraint programming, computational linguistics and in concrete applications like software configuration management. Feature trees model records, and constraints over feature trees yield extensible and modular record descriptions. We introduce the constraint system FT of ordering constraints interpreted over feature trees. Under the view that feature trees represent symbolic information, the relation corresponds to the information ordering ("carries less information than"). We present two algorithms in cubic time, one for the satisfiability problem and one for the entailment problem of FT . We show that FT has the independence property. We are thus able to handle negative conjuncts via entailment and obtain a cubic algorithm that decides the satisfiability of conjunctions of positive and negated ordering constraints over feature trees. Furthermore, we reduce the satisfiability problem of Dorre's weak subsumption constraints to the satisfiability problem of FT and improve the complexity bound for solving weak subsumption constraints from O(n^5) to O(n³).
NonStructural Subtype Entailment in Automata Theory
, 2003
"... Decidability of nonstructural subtype entailment is a longstanding open problem in programming language theory. In this paper, we apply automata theoretic methods to characterize the problem equivalently by using regular expressions and word equations. This characterization induces new results on ..."
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Cited by 8 (3 self)
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Decidability of nonstructural subtype entailment is a longstanding open problem in programming language theory. In this paper, we apply automata theoretic methods to characterize the problem equivalently by using regular expressions and word equations. This characterization induces new results on nonstructural subtype entailment, constitutes a promising starting point for further investigations on decidability, and explains for the first time why the problem is so difficult. The difficulty is caused by implicit word equations that we make explicit.
Entailment of nonstructural subtype constraints
 in: Asian Computing Science Conference, Lecture Notes in Computer Science 1742
, 1999
"... Abstract. Entailment of subtype constraints was introduced for constraint simplification in subtype inference systems. Designing an efficient algorithm for subtype entailment turned out to be surprisingly difficult. The situation was clarified by Rehof and Henglein who proved entailment of structur ..."
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Cited by 5 (4 self)
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Abstract. Entailment of subtype constraints was introduced for constraint simplification in subtype inference systems. Designing an efficient algorithm for subtype entailment turned out to be surprisingly difficult. The situation was clarified by Rehof and Henglein who proved entailment of structural subtype constraints to be coNPcomplete for simple types and PSPACEcomplete for recursive types. For entailment of nonstructural subtype constraints of both simple and recursive types they proved PSPACEhardness and conjectured PSPACEcompleteness but failed in finding a complete algorithm. In this paper, we investigate the source of complications and isolate a natural subproblem of nonstructural subtype entailment that we prove PSPACEcomplete. We conjecture (but this is left open) that the presented approach can be extended to the general case.
Entailment with conditional equality constraints
 In Proceedings of European Symposium on Programming
, 2001
"... Abstract Equality constraints (unification constraints) have widespread use in program analysis, most notably in static polymorphic type systems. Conditional equality constraints extend equality constraints with a weak form of subtyping to allow for more accurate analyses. We give a complete complex ..."
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Cited by 4 (4 self)
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Abstract Equality constraints (unification constraints) have widespread use in program analysis, most notably in static polymorphic type systems. Conditional equality constraints extend equality constraints with a weak form of subtyping to allow for more accurate analyses. We give a complete complexity characterization of the various entailment problems for conditional equality constraints and for a natural extension of conditional equality constraints.
Atomic Set Constraints with Projection
, 2002
"... We investigate a class of set constraints defined as atomic set constraints... ..."
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We investigate a class of set constraints defined as atomic set constraints...