Languages that capture complexity classes
SIAM Journal on Computing
Foundations of logic programming; (2nd extended ed.)
Foundations of logic programming; (2nd extended ed.)
Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
Towards a theory of declarative knowledge
Foundations of deductive databases and logic programming
Recursive query processing: the power of logic
Theoretical Computer Science
The expressive power of stratified logic programs
Information and Computation
Well-founded semantics coincides with three-valued stable semantics
Fundamenta Informaticae
Datalog extensions for database queries and updates
Journal of Computer and System Sciences
Journal of Computer and System Sciences
A catalog of complexity classes
Handbook of theoretical computer science (vol. A)
Journal of the ACM (JACM)
The well-founded semantics for general logic programs
Journal of the ACM (JACM)
Stable and extension class theory for logic programs and default logics
Journal of Automated Reasoning
General patterns in nonmonotonic reasoning
Handbook of logic in artificial intelligence and logic programming (vol. 3)
Modular stratification and magic sets for Datalog programs with negation
Journal of the ACM (JACM)
A syntactic stratification condition using constraints
ILPS '94 Proceedings of the 1994 International Symposium on Logic programming
Structural totality and constraint stratification
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The expressive powers of stable models for bound and unbound DATALOG queries
Journal of Computer and System Sciences - special issue on complexity theory
The expressive powers of the logic programming semantics (extended abstract)
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Stable models and non-determinism in logic programs with negation
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Non-deterministic languages to express deterministic transformations
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Non-determinism and weak constraints in datalog
New Generation Computing
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
"Possible is certain'' is desirable and can be expressive
Annals of Mathematics and Artificial Intelligence
Dynamic Programming in Datalog with Aggregates
IEEE Transactions on Knowledge and Data Engineering
DATALOG Queries with Stratified Negation and Choice: from P to DP
ICDT '95 Proceedings of the 5th International Conference on Database Theory
Total and Partial Well-Founded Datalog Coincide
ICDT '97 Proceedings of the 6th International Conference on Database Theory
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
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A 'functional' query is a query whose answer is always defined and unique i.e. it is either true or false in all models. It has been shown that the expressive powers of the various types of stable models, when restricted to the class of DATALOG functional queries, do not in practice go beyond those of well-founded semantics, except for the least undefined stable models which, instead, capture the whole boolean hierarchy BH.In this paper we present a 'functional' language which, by means of a disciplined use of negation, achieves the desired level of expressiveness up to BH. Although the semantics of the new language is partial, all atoms in the source program are defined and possibly undefined atoms are introduced in a rewriting phase to increase the expressive power. We show that the language satisfies 'desirable' properties better than classical languages with (unstratified) negation and stable model semantics. We present an algorithm for the evaluation of functional queries and we show that exponential time resolution is required for hard problems only. Finally we present the architecture of a prototype of the language which has been developed.