Abstract:
In this thesis, we investigate the use of sets in the relational model. In particular, we look at two separate appproaches. The first approach involves using collective sets as a collection of discrete data elements, while the second approach involves using disjunctive sets to represent incomplete information. We generalize these two approaches, proposing generalized sets, and consider a relational model which combines all three types of set — collective, disjunctive and generalized. Finally, we present a further generalization of the above approaches and introduce a relational model with restricted cardinality set. In this model, we explicitly store the minimum and maximum number of actual values in each set. This results in a model which is more simple, flexible, and enhances the richness of information that can be represented.
