Inductive Pebble Games and the Expressive Power of Datalog

@inproceedings{Lakshmanan1989InductivePG,
  title={Inductive Pebble Games and the Expressive Power of Datalog},
  author={Laks V. S. Lakshmanan and Alberto O. Mendelzon},
  booktitle={PODS},
  year={1989}
}
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… CONTINUE READING
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