Object-Orientation FAQ

3.5) What Are Object-Oriented Databases And Persistence?

See also Appendices B and E and the comp.database.object newsgroup.
Refs to be included in future FAQs.
Object-Oriented Databases are databases that support objects and classes.  They
are different from the more traditional relational databases because they allow
structured subobjects, each object has its own identity, or object-id (as
opposed to a purely value-oriented approach) and because of support for methods
and inheritance.  It is also possible to provide relational operations on an
object-oriented database.  OODBs allow all the benefits of object-orientation,
as well as the ability to have a strong equivalence with object-oriented
programs, an equivalence that would be lost if an alternative were chosen, as
with a purely relational database.
Another way of looking at Object-Oriented Databases is as a persistent object
store with a DBMS.
Persistence is often defined as objects (and their classes in the case of
OODBs) that outlive the programs that create them.  Object lifetimes can be
viewed as a hierarchy, with locals/automatics having the shortest default
lifetime and objects stored indefinitely in an OODB (which are persistent)
having the longest.  Persistent object stores do not support query or
interactive user interface facilities, as found in a fully supported OODBMS.
Appendix B also contains references for object-oriented interfaces to
relational databases and see APPENDIX E, Papers, Persistent Operating Systems.
From the net:
From: dbmsfacts@aol.com (DBMSfacts)
Subject: ODMG Gopher and Web Addresses
Date: 24 Oct 1994 13:10:02 -0400
The Object Database Management Group (ODMG) has set up Gopher and Web
Servers at the following addresses:
  Gopher:  gopher.odmg.org, port 2073
  WWW:  http://www.odmg.org:3083
These are still under construction.  What you can find right now are
addresses and contact information for ODBMS vendors, ODMG membership
information, updates to Release 1.1 of The Object Database Standard:
ODMG-93 along with ODL lex and yacc files.  In the future, we will be
adding more links to related sites, bibliographies, and a FAQ for ODBMSs. 
If you cannot access these servers, but would like information on the
ODMG, send an email message to info@odmg.org and you will receive an
automated reply.
Doug Barry
ODMG Executive Director

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