Abstract:
This short paper introduces possibilistic functional dependencies.
These dependencies are associated with a particular possibility distribution
over possible worlds of classical database. The possibility
distribution reflects a layered view of the database. The highest layer
of the (classical) database consists of those tuples which certainly belong
to it, while the other layers add tuples that only possibly belong
to the database, with different levels of possibility. The relation between
the confidence levels associated with the tuples and the possibility
distribution over possible database worlds is discussed in detail
in the setting of possibility theory. A possibilistic functional dependency
is a classical functional dependency associated with a certainty
level that reflects the highest confidence level where the functional
dependency no longer holds in the layered database. Moreover, the
relationship between possibilistic functional dependencies and possibilistic
logic formulas is established. Related work is reviewed, and
the intended use of possibilistic functional dependencies is discussed
in the conclusion.
