Many object oriented data models have been proposed in the past few ye
ars, and this field is one of the most promising for the development o
f new generation database systems. With complex data structures where
an ISA hierarchy has been defined, the problem of efficiently storing
and retrieving (a collection of) objects increases its relevance drama
tically. This paper proposes efficient set-oriented algorithms for the
storage and retrieval of complex objects in an inheritance hierarchy.