Object-oriented database management systems (OODBMS) are used to imple-
ment and maintain large object databases on persistent storage.
Regardless whether the underlying database model follows the
object-oriented, the rela- tional or the object-relational paradigm, a
key feature of any DBMS product is content based access to data sets. On
the one hand this feature provides user-friendly query interfaces based
on predicates to describe the desired data. On the other hand it poses
challenging questions regarding DBMS design and implementation as well
as the application development process on top of the DBMS. The reason
for the latter is that the actual query performance depends on a
technically meaningful use of access support mechanisms. In particular,
if chosen and applied properly, such a mechanism speeds up the execution
of predicate based queries. In the object-oriented world, such queries
may involve arbitrarily complex terms referring to inheritance
hierarchies and aggregation paths. These features are attractive at the
application level, however, they increase the complexity of appropriate
access support mechanisms which are known to be technically non-trivial
in the relational world.