Database Reference
In-Depth Information
It is worth noting that, under the
card
-minimal semantics, the complexity of
MRC
and
CQA
does not depend on the numerical data domain and the class of aggregate
constraint considered. This does not hold under the
set
-minimal semantics.
Interestingly enough, while, in general, the complexity of
CQA
under the
set
-
minimal semantics is higher than the case of
card
-minimal semantics, the
CQA
problem under
set
-minimal semantics becomes easier than the same problem un-
der
card
-minimal semantics in the presence of steady aggregate constraints, if the
numerical data are rationals. Moreover, for this class of constraints and this numer-
ical domain, also the complexity of the
MRC
problem under
set
-minimal semantics
becomes lower than that of the
MRC
problem under
card
-minimal semantics.
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