Alternation and the computational complexity of logic programs
Journal of Logic Programming
A graphical query language supporting recursion
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
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
Journal of the ACM (JACM)
Relational queries computable in polynomial time (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
On Datalog vs. polynomial time (extended abstract)
PODS '91 Proceedings of the tenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
QBD*: A Graphical Query Language with Recursion
IEEE Transactions on Software Engineering
Datalog expressiveness of chain queries: grammar tools and characterizations
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Monotone monadic SNP and constraint satisfaction
STOC '93 Proceedings of the twenty-fifth annual ACM symposium on Theory of computing
Combinatorial games in database theory
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
On the expressive power of datalog: tools and a case study
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Inherent complexity of recursive queries
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Complexity and expressive power of logic programming
ACM Computing Surveys (CSUR)
Annals of Mathematics and Artificial Intelligence
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As an alternative to logic-based query languages for recursive queries, we are investigating a graphical query language called G+, which allows, among other things, easy formulation of certain queries involving simple paths in directed graphs. This led us to study whether such queries are expressible in DATALOG, the language of function-free Horn clauses. Since some G+ queries are NP-hard, and all DATALOG queries are polynomial time computable, the answer appears to be negative. However, it would be interesting to have proof techniques and tools for settling such questions with certainty. The objective of this paper is the development of one such tool, inductive pebble games, based on a normal form for DATALOG programs derived here, and its relationship to Alternating Turing Machine computations. As an application, we sketch a proof that the query “find all pairs of nodes connected by a directed simple path of even length” cannot be expressed in DATALOG.