Database queries explicitly containing existential
and universal quantification become increasingly important
in a number of areas such as integrity checking, interaction
of databases, and statistical databases. Using a
concept of range nesting in relational calculus expressions,
the paper describes evaluation algorithms and transformation
methods for an important class of quantified relational calculus
queries called perfect expressions. This class includes
well-known classes of "easy" queries such as tree queries
(with free and existentially quantified variables only), and
complacent (disconnected) queries.Information Systems Working Papers Serie