Publisher Summary This chapter presents a systematic and unifying introduction to
relational database theory, including some of the recent developments in database logic …

Bags, ie sets with duplicates, are often used to implement relations in database systems. In
this paper we study the expressive power of algebras for manipulating bags. The algebra we …

Nested relations generalize ordinary flat relations by allowing tuple values to be either
atomic or set valued. The nested algebra is a generalization of the flat relational algebra to …

We propose an object-oriented data model that generalizes the relational, hierarchical, and
network models. A database scheme in this model is a directed graph, whose leaves …

The set-height of a complex object type is defined to be its level of nesting of the set
construct. In a query of the complex object calculus which maps a database D to an output …

Several alternative semantics (or interpretations) of the relational (domain) calculus are
studied here. It is shown that they all have the same expressive power, ie, the selection of …

Conventional database query languages are considered in the context of untyped sets. The
algebra without while has the expressive power of the typed complex object algebra. The …

The expressiveness and complexity of several calculus-based query languages for complex
objects is considered. Unlike previous investigations, we are concerned with the complexity …

Four database modeling paradigms are compared along a number of dimensions, including
their treatment of 'object identity'; issues of redundant structure and/or data; the notions of …

In the present article, we study the expressive power of higher-order logics on finite
relational structures or databases. First, we give a characterization of the expressive power …