Languages that capture complexity classes
SIAM Journal on Computing
Foundations of logic programming; (2nd extended ed.)
Foundations of logic programming; (2nd extended ed.)
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)
The alternating fixpoint of logic programs with negation
PODS '89 Selected papers of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Stable and extension class theory for logic programs and default logics
Journal of Automated Reasoning
The expressive powers of the logic programming semantics
Selected papers of the 9th annual 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
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
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
Programming with non-determinism in deductive databases
Annals of Mathematics and Artificial Intelligence
DATALOG Queries with Stratified Negation and Choice: from P to DP
ICDT '95 Proceedings of the 5th International Conference on Database Theory
Generalized Implicit Definitions on Finite Structures
CSL '95 Selected Papers from the9th International Workshop on Computer Science Logic
The Expressive Power of Partial Models in Disjunctive Deductive Databases
LID '96 Proceedings of the International Workshop on Logic in Databases
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
New Generation Computing
Declarative semantics for active rules
Theory and Practice of Logic Programming
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The partial stable models of a logic program form a class of models that include the (unique) well-founded model, total stable models and other two interesting subclasses: maximal stable models and least undefined stable models. As stable models different from the well-founded are not unique, DATALOG queries do not in general correspond to functions. The question is: what are the expressive powers of the various types of stable models when they are restricted to the class of all functional queries? The paper shows that this power does not go in practice beyond the one of stratified queries, except for least undefined stable models which, instead, capture the whole Boolean hierarchy BH. Finally, it is illustrated how the latter result can be used to design a ``functional'' language which, by means of a disciplined usage of negation, allows to achieve the desired level of expressiveness up to BH so that exponential time resolution is eventually enabled only for hard problems.