Proceedings of the Second European Symposium on Programming
ACM Transactions on Programming Languages and Systems (TOPLAS)
A feature constraint system for logic programming with entailment
FGCS'921 Selected papers of the conference on Fifth generation computer systems
Sound polymorphic type inference for objects
Proceedings of the tenth annual conference on Object-oriented programming systems, languages, and applications
Simplifying subtyping constraints
Proceedings of the first ACM SIGPLAN international conference on Functional programming
Foundations of programming languages
Foundations of programming languages
Minimal typings in atomic subtyping
Proceedings of the 24th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
A framework for type inference with subtyping
ICFP '98 Proceedings of the third ACM SIGPLAN international conference on Functional programming
Ordering Constraints over Feature Trees
Constraints
Constraint Automata and the Complexity of Recursive Subtype Entailment
ICALP '98 Proceedings of the 25th International Colloquium on Automata, Languages and Programming
SAS '96 Proceedings of the Third International Symposium on Static Analysis
Set constraints with intersection
LICS '97 Proceedings of the 12th Annual IEEE Symposium on Logic in Computer Science
The complexity of subtype entailment for simple types
LICS '97 Proceedings of the 12th Annual IEEE Symposium on Logic in Computer Science
The First-Order Theory of Ordering Constraints over Feature Trees
LICS '98 Proceedings of the 13th Annual IEEE Symposium on Logic in Computer Science
Entailment of Atomic Set Constraints is PSPACE-Complete
LICS '99 Proceedings of the 14th Annual IEEE Symposium on Logic in Computer Science
Feature logic with weak subsumption constraints
ACL '91 Proceedings of the 29th annual meeting on Association for Computational Linguistics
Non-structural Subtype Entailment in Automata Theory
TACS '01 Proceedings of the 4th International Symposium on Theoretical Aspects of Computer Software
Complexity of subtype satisfiability over posets
ESOP'05 Proceedings of the 14th European conference on Programming Languages and Systems
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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 coNP-complete for simple types and PSPACE-complete for recursive types. For entailment of non-structural subtype constraints of both simple and recursive types they proved PSPACE-hardness and conjectured PSPACE-completeness but failed in finding a complete algorithm. In this paper, we investigate the source of complications and isolate a natural subproblem of non-structural subtype entailment that we prove PSPACE-complete. We conjecture (but this is left open) that the presented approach can be extended to the general case.