Databases Reference
In-Depth Information
Update processing. Three issues are relevant here: the kind of updates
allowed by each system, that is, updates of base facts and/or view
updates; the applications of change computation provided, that is,
materialized view maintenance (MVM), integrity constraint check-
ing (ICC), or condition monitoring (CM); and the integrity con-
straint enforcement policy, that is, ICC or integrity constraint
maintenance (ICM).
·
Storage. It states whether the EDB, the IDB, or both are kept on sec-
ondary storage.
·
As shown in Table 4.2, most deductive DBMSs have concentrated on
providing efficient techniques for the storage and retrieval of large amounts
of complex data. Thus, just a few current deductive DBMSs provide some
mechanism for advanced data updating, other than updates of base facts. To
our fair knowledge, only EKS-V1, FOLRE, and the two prototypes devel-
oped into the IDEA project incorporate advanced update capabilities. On
the other hand, systems providing advanced update capabilities have
deserved little attention to query processing issues and rely on a back end that
fully provides the support for query evaluation needs, or they are not able to
evaluate queries efficiently.
4.6
Summary
Deductive DBs contain intensional information, expressed as views and
integrity constraints, in addition to extensional information. Therefore, they
require a query and an update processing system able to deal with that kind
of information. This chapter presented several problems encountered when
dealing at run time with intensional information, like query processing,
change computation, view updating, or integrity constraint enforcement,
and provided an overview of previous research in this area.
While techniques developed as a result of the research in deductive DBs
have been incorporated into current relational technology, there is no deduc-
tive DBMS in commercial use. A possible reason is that although most
deductive prototypes provide efficient techniques for query processing,
update processing has not been extensively considered. Therefore, the most
distinguishing feature of deductive technologythe update and manage-
ment
of
intensional
informationis
not
fully
provided
by
existing
prototypes.
