Hypertree decompositions and tractable queries

@inproceedings{Gottlob1999HypertreeDA,
  title={Hypertree decompositions and tractable queries},
  author={Georg Gottlob and Nicola Leone and Francesco Scarcello},
  booktitle={ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems},
  year={1999}
}
1 A preliminary version of this paper appeared in the ‘‘Proceedings of the Eighteenth ACM Symposium on Principles of Database Systems (PODS’99),’’ pp. 21–32, Philadelphia, May 1999. Research supported by FWF (Austrian Science Funds) under the Project Z29-INF. Part of the work of Francesco Scarcello has been carried out while visiting the Technische Universitat Wien. Part of the work of Nicola Leone has been carried out while he was with the Technische Universitat Wien. Georg Gottlob 

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References

SHOWING 1-10 OF 85 REFERENCES

On the complexity of database queries (extended abstract)

It is shown that, if the query size (or the number of variables in the query) is considered as a parameter, then the relational calculus and its fragments are classified at appropriate levels of the so-called W hierarchy of Downey and Fellows.

On the Complexity of Database Queries

It is shown that, if the query size (or the number of variables in the query) is considered as a parameter, then the relational calculus and its fragments are classified at appropriate levels of the so-called W hierarchy of Downey and Fellows.

Decomposing Constraint Satisfaction Problems Using Database Techniques

Tree Clustering for Constraint Networks

The complexity of acyclic conjunctive queries

We show that the problem of evaluating acylic Boolean database-queries is LOGCFL-complete and thus highly parallelizable. We present a parallel database algorithm solving this problem with a

Power of Natural Semijoins

This paper characterizes the queries for which full reducer exist and presents an efficient algorithm for constructing full reducers where they do exist and considers “natural” semijoin operator, which is used in the SDD-1 distributed database system.

Algorithms for Acyclic Database Schemes

The purpose in this paper is to describe efficient algorithms in this setting for various problems, such as computing projections, minimizing joins, inferring dependencies, and testing for dependency satisfaction.

On the Desirability of Acyclic Database Schemes

It is shown that this class of database schemes, called acychc, has a number of desirable properties that have been studied by other researchers and are shown to be eqmvalent to acydicity.

On Tractable Queries and Constraints

This paper surveys recent results by the authors on tractable classes of conjunctive queries and constraint satisfaction problems and presents a new decomposition algorithm for such problems.

Optimal implementation of conjunctive queries in relational data bases

It is shown that while answering conjunctive queries is NP complete (general queries are PSPACE complete), one can find an implementation that is within a constant of optimal.
...