Selected papers of the 9th annual ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Variable independence and aggregation closure
PODS '96 Proceedings of the fifteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The DEDALE system for complex spatial queries
SIGMOD '98 Proceedings of the 1998 ACM SIGMOD international conference on Management of data
Constraint Databases
Variable independence for first-order definable constraints
ACM Transactions on Computational Logic (TOCL)
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A formula &psgr; (x1,...,xn) conforms to a partition P of {x 1, ...,xn} if is equivalent to a Boolean combination of formulae that do not have free variables from more than one block of P. We show that if &psgr; conforms to two partitions P1 and P1 and P2, it also conforms to their greatest lower bound in the partition lattice. As a corollary, we obtain that the concept of orthographic dimension of a constraint-definable set, introduced in the field of constraint databases, is well-defined. 2001 Elsevier Science B.V. All rights reserved.