1 research outputs found
Approximate Integrity Constraints in Incomplete Databases With Limited Domains
In case of incomplete database tables, a possible world is obtained by
replacing any missing value by a value from the corresponding attribute's
domain that can be infinite. A possible key or possible functional dependency
constraint is satisfied by an incomplete table if we can obtain a possible
world that satisfies the given key or functional dependency. On the other hand,
a certain key or certain functional dependency holds if all possible worlds
satisfy the constraint, A strongly possible constraint is an intermediate
concept between possible and certain constraints, based on the strongly
possible world approach (a strongly possible world is obtained by replacing
\nul's by a value from the ones appearing in the corresponding attribute of the
table). A strongly possible key or functional dependency holds in an incomplete
table if there exists a strongly possible world that satisfies the given
constraint. In the present paper, we introduce strongly possible versions of
multivalued dependencies and cross joins, and we analyse the complexity of
checking the validity of a given strongly possible cross joins. We also study
approximation measures of strongly possible keys (spKeys), functional
dependencies (spFDs), multivalued dependencies (spMVDs) and cross joins
(spCJs). We also treat complexity questions of determination of the
approximation values