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Subject: Comp.Object FAQ Version 1.0.6 (9-15) Part 4/9
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Summary: Frequently Asked Questions (FAQ) List and Available Systems For Object-Oriented Technology
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Archive-name: object-faq/part4
Last-Modified: 9/15/94
Version: 1.0.6

The Montage object-relational database management system
includes the Montage Server(tm) database engine, the Montage
Viewer(tm) -- a new visualization tool that simplifies queries of
complex data -- and Montage DataBlades(tm), specialized modules
that extend the capabilities of the database for specific applications.
Montage represents the commercialization of the seven-year
POSTGRES research project.

The Montage Server extends the relational database model through
its ability to handle complex information, and the inclusion of object-
oriented facilities and capabilities.  It uses the familiar relational row-
column metaphor for all data, so that text, numbers and complex data
are all viewed, managed, manipulated and queried the same way.
The relational metaphor is extended to allow data of any size and
complexity to be stored and accessed in the way that is most
effective.   SQL, used to access and manage data, is extended with
SQL3-based capabilities to allow the definition of user data types and
functions.

The Montage Viewer uses visualization technology to organize
information in visual terms -- by location, shape, color and intensity,
for example.  Similar to a "flight simulator," the Montage Viewer allows
the user to visually navigate through data, refining each step by
"panning" and "zooming" with a mouse.

A DataBlade is a combination of data types and functions that are
designed to support a specific application.   Text, Spatial, and Image
are the first of many DataBlades that will comprise a full-range of
industry-specific products created by Montage, third parties and
users based upon their own expertise.

o     The Text DataBlade expands the database's functionality by
adding new data types and functions that manage text and document
libraries, as well as a providing a new access method (Doc-Tree)
which provides exceptional search performance for text.

o     The Image DataBlade supports image conversion, storage,
manipulation, enhancement and management of more than 50 image
formats, and performs automatic conversion of formats at the user's
discretion.

o     Points, lines, polygons and their spatial relationships are now
supported in the relational model with the Spatial DataBlade.  The
DataBlade defines nine basic spatial types and makes over 200 SQL
functions available for use on spatial data, as well as supports the
R-Tree access method for high speed navigation of spatial data.

Montage Software was co-founded by Gary Morgenthaler of
Morgenthaler Ventures and Dr. Michael Stonebraker of the University
of California, Berkeley, .  Morgenthaler is Montage Software's
chairman of the board and Stonebraker serves as the company's
chief technology officer.    Morgenthaler and Stonebraker co-
founded Ingres Corporation (then called Relational Technology,
Inc.), in 1980.

FOR ADDITIONAL INFORMATION:

Montage Software Inc. can be contacted at:

email:                        [e-mail]
phone:                        [phone]
fax:                          [phone]

Mailing Address:

Montage Software, Inc.
2000 Powell Street, Suite 1405
Emeryville, CA  94608

OO DATA MODEL
-------------

Research Systems
________________

> AVANCE (SYSLAB)

An object-oriented, distributed database programming language.  Its
most interesting feature is the presence of system-level version
control, which is used to support schema evolution, system-level
versioning (as a way of improving concurrency), and objects with their
own notion of history.  System consists of programming language (PAL)
and distributed persistent object manager.

REFERENCES:
        Anders Bjornerstedt and Stefan Britts. "AVANCE: An
        Object Management System".  Proceedings of OOPSLA88.



> CLOSQL (University of Lancaster)

Status:-
CLOSQL is a research prototype OODB designed primarily for prototyping
various schema evolution and view mechanisms based on class versioning.
The system is built using CommonLISP. It would really only be of interest
to other parties as a research tool.

Requirements:-
Common LISP including CLOS standard. The Graphical user interface requires
the Harlequin LispWorks Tool-kit. The system was built on a Sun4 and
has not been tested on any other platform.

Features:-
As a prototype, CLOSQL is not robust enough to sell. The system is single
user and does not properly support persistence - that is, the data has to
be loaded and saved explicitly. The query language is quite good
making good use of the functional nature of the environment.
Methods (LISP and query language only), class versioning and
multiple inheritance are all supported in the data model. Type checking
information is held in the database, but is NOT enforced at present. The
GUI is notable for its support for schema evolution, but otherwise rather
ordinary.

Availability:-
Probably freely available, but as the project was part funded by an
industrial partner, some consultation with them would be necessary before
the system could be released.

References:-
[1]  Monk, S. R. and I. Sommerville, "A Model for Versioning of Classes
in Object-Oriented Databases", Proceedings of BNCOD 10, Aberdeen.
pp.42-58. 1992.

[2]  Monk, S. "The CLOSQL Query Language". Technical report No. SE-91-15.
Computing Dept, Lancaster University, Lancaster, LA1 4YR, UK. 1991.

[3]  Monk, S., "A Model For Schema Evolution In Object-Oriented Database
Systems", PhD thesis, Dept of Computing, Lancaster University, Lancaster
LA1 4YR, UK. 1992.

On Schema evolution (from original survey):
CLOSQL implements a class versioning scheme (like ENCORE), but employs a
conversion adaptation strategy.  Instances are converted when there is a
version conflict, but unlike ORION and GemStone, CLOSQL can convert instances
to older versions of the class if necessary.

        Aberdeen, Scotland. July, 1992.

Contacts;
Simon Monk:      [e-mail]
Ian Sommerville: [e-mail]


> ConceptBase - A Deductive Object Manager for Meta Data Bases

ConceptBase is a multi-user deductive object manager mainly
intended for conceptual modeling and the coordination of design
environments. The system implements a dialect of Telos which
amalgamates properties of deductive and object-oriented languages.

Key features are

   hybrid representation with frame-like objects,
   semantic nets and logical specifications

   unlimited extensibility by metaclass
   hierarchies (useful for IRDS, schema evolution etc.)

   deductive rules & integrity constraints

   queries as classes with membership constraints

   persistent object management with the ability to interrogate
   past states of the database

ConceptBase follows a client-server architecture. Client programs
can connect to the ConceptBase server and exchange data via
interprocess communication. The X11-based ConceptBase user
interface offers a palette of graphical, tabular and textual tools
for editing and browsing the object base. The ConceptBase
programming interface allows the users to create their own
client programs in C or Prolog.

The system can be obtained for free from ftp.informatik.rwth-aachen.de in
      /pub/CB/CB_3.2.4 (released 26-Apr-1994 for Sun/SPARC, SunOS 4.1.3)
      /pub/CB/CB_3.3 (released 26-Apr-1994 for Sun/SPARC, Solaris 2.3)
Both versions are functionally equivalent. They only differ in the
operating system platform.Please read file /pub/CB/doc/InstallationGuide
(resp. /pub/CB/doc/InstallationGuide_3.2.4) before downloading the software.
For running the ftp version you must ask for a key by email.

Contact
ConceptBase-Team
RWTH Aachen - Informatik V
D-52056 Aachen - Germany

Tel./Fax: [phone]
email: [e-mail]
href="http://www.informatik.rwth-aachen.de/I5/CBdoc/cbflyer.html"


> COOL/COCOON (Ulm Universitaet)

The COCOON project was intended to extend the concepts and the
architecture of relational database management systems (DBMSs) beyond
nested relational to object-oriented ones. Based upon the nested
relational DBMS kernel DASDBS, we have built a prototype implementation
of the COCOON model. Key characteristics of COCOON are: generic,
set-oriented query and update operators similar to relational algebra
and SQL updates, respectively; object-preserving semantics of query
operators, which allows for the definition of updatable views; a
separation of the two aspects of programming language "classes": type
vs. collection; predicative description of collections, similar to
"defined concepts" in KL-One--like knowledge representation
languages; automatic classification of objects and views (positioning
in the class hierarchy); physical clustering of subobjects via the use
of nested relations as the internal storage structures; support for the
optimization of both, the physical DB design and query transformation,
by corresponding optimizers.

Project goals are:

- to develop a general formal framework for investigations of all
  kinds of schema changes in object-oriented database systems
  (including schema design, schema modification, schema tailoring, and
  schema integration);
- to find implementation techniques for evolving database schemas,
  such that changes on the logical level propagate automatically to
  adaptations of the physical level (without the need to modify all
  instances, if possible).

In their current paper [see below], schema evolution is used as
example of a general framework for change in OODBs, supporting change
on three levels of database objects: data objects, schema objects, and
meta-schema objects.

Contact: Markus Tresch <[e-mail]>


REFERENCES:
        M. Tresch and M.H. Scholl. "Meta Object Management
        and its Application to Database Evolution."  In
        _Proceedings of the Eleventh International
        Conference on the Entity-Relationship Approach",
        Karlsruhe, Germany, Oct 1992.  Springer Verlag (to
        appear).



> Encore (Brown University)
email:[e-mail]

Encore is an object-oriented database system targeted at large scale
software engineering applications which are involved in data modeling.
It was developed at Brown University in the late 1980s.  It is notable
for its special support for long-lived (ie. cooperative) transactions,
popular in design applications, and its support for class versioning.
Objects are never converted, rather, classes are versioned, and the
user can specify filters to make old-style instances appear as new
instances to new applications (and vice versa).


References/Additional Information:

 [] Mary F. Fernandez. OBSERVER: A storage system
    object-oriented applications. Technical Report CS-90-27,
    Brown University, Providence, RI, 1990.

 [] Mark F. Hornick and Stanley B. Zdonik. A shared, segmented
    memory system for an object-oriented database. ACM
    Transactions on Office Information Systems, 5(1):70--95,
    January 1987.

 [] Andrea H. Skarra and Stanley B. Zdonik. Type evolution in an
    object-oriented database. In Research Directions in
    Object-Oriented Programming, MIT Press Series in Computer
    Systems, pages 393--415. MIT Press, Cambridge, MA, 1987. An
    early version of this paper appears in the OOPSLA '86
    proceedings.

 [] Andrea H. Skarra and Stanley B. Zdonik. Concurrency control
    for cooperating transactions in an object-oriented database.
    In Won. Kim and Frederick H. Lochovsky, editors,
    Object-Oriented Concepts, Databases and Applications.
    Addison-Wesley, Reading, MA, 1989.

FTP: Complete source can be found in wilma.cs.brown.edu/pub/encore.tar.Z
See also APPENDIX E.


> Exodus (University of Wisconsin)

EXODUS is a DBMS from the University of Wisconsin.  An overview,
excerpted from the abstract of [CDG+90] reads:

    EXODUS,   an   extensible database    system  project that is
    addressing  data management problems  posed  by  a variety of
    challenging new applications.  The  goal of the project is to
    facilitate   the   fast    development of   high-performance,
    application-specific  database  systems.     EXODUS  provides
    certain  kernel facilities,   including  a versatile  storage
    manager.  In addition, it provides an architectural framework
    for building  application-specific database systems; powerful
    tools   to  help  automate the  generation   of such systems,
    including  a   rule-based query optimizer generator    and  a
    persistent  programming  language;  and libraries  of generic
    software components (e.g., access methods) that are likely to
    be useful for many application domains.

The programming language is called E, an extension of C++. [RC89]

REFERENCES:
(see "ftp.cs.wisc.edu:exodus/bibliography" for a complete list)

[CDG+90] Michael J. Carey, David J. DeWitt, Goetz Graefe,
         David M. Haight, Joel E. Richardson, Daniel T. Schuh,
         Eugene J. Skekita, and Scott L. Vandenberg. The EXODUS
         extensible DBMS project:  An overview. In Stanley B.
         Zdonik and David Maier, editors, Readings in
         Object-Oriented Database Systems, Data Management
         Series. Morgan Kaufmann, San Mateo, CA, 1990. Also
         available as WISC-CS-TR 808.

[CDRS89] Michael J. Carey, David J. DeWitt, Joel E. Richardson,
         and Eugene J. Skekita. Storage management for objects
         in EXODUS. In Won. Kim and Frederick H. Lochovsky,
         editors, Object-Oriented Concepts, Databases and
         Applications, chapter 14. Addison-Wesley, Reading, MA,
         1989. After Carey et al. Object and File Management in
         the EXODUS Database System, Proceedings of the Twelveth
         International Conference on Very Large Data Bases,
         1986.

[GD87]   G. Graefe and D. DeWitt. The EXODUS optimizer
         generator. In U. Dayal and I. Traiger, editors,
         Proceedings of the SIGMOD International Conference on
         Management of Data, San Francisco, CA, May 1987.

[RC89]   Joel E. Richardson and Michael J. Carey. Persistence in
         the E language:  Issues and implementation. Software --
         Practice and Experience, 19(12):1115--1150, December
         1989.


FTP: source code, documentation and a complete bibliography can be
     found at ftp.cs.wisc.edu:exodus/

See also APPENDIX E.


On Schema Evolution (from original survey):
No solution for the problem of schema evolution is provided.
Emulation is rejected by the authors, who claim that the addition of a
layer between the EXODUS Storage Manager and the E program would
seriously reduce efficiency.  Automatic conversion, whether lazy or
eager, is also rejected, as it does not mesh well with the C++ data
layout.  To implement immediate references to other classes and
structures, C++ embeds class and structure instances within its
referent.  The resulting change in the size of the object might
invalidate remote pointer references.

        Joel E.  Richardson and Michael J.  Carey.  "Persistence
        in the E language: Issues and Implementation."  Appeared
        in "Software -- Practice and Experience",
        19(12):1115-1150, December 1989.


> Machiavelli (University of Pennsylvania)

Machiavelli is a statically-typed programming language developed
at the University of Pennsylvania. Its most outstanding innovation
is the use of conditional typing scheme in its type inference system.
It does not address type evolution.

[communication with [e-mail]]

[Note: Machiavelli is included in this summary because it
       previously incorporated persistence in its data model.]



> MOOD4-PC: Material's/Miniature Object-Oriented Database Prototype for
             NEC/IBM-PC

is an object-oriented database system(OODBS) program developed in the
course of our research project MOOD. The aim of the project MOOD is to
develop a material database system to handle raw material data which
are produced and accumulated in materials research and referred to by
material experts when they face scientific or engineering problems
where the expected behavior of particular materials in particular
environments are crucial importance. We all know that the conventional
database systems do not fulfill this requirement, though they serves
well for bibliographic databases or fact databases which deals with
the standard properties of standard materials.

MOOD4-PC is written in Arity/Prolog and available in source and
executable form via anonymous ftp from:

   ~/pub/mood/mood4
   at mood.mech.tohoku.ac.jp [130.34.88.61]

    ~/pub/database/mood
    at ftp.uu.net [192.48.96.9]

    ~/pub/computing/databases/mood
    at src.doc.ic.ac.uk [146.169.2.1]

Although it is true enough to say that MOOD4 is a general purpose
OODBS, it may be appropriate to point out that MOOD4 is significantly
different from what is generally meant by the term, the
Object-Oriented Database System.

That is, OODBSs, in general, consist of two parts:

   (1) Disk storage manager
   (2) Database language to define and manipulate data objects to
       be stored to and retrieved from the disk.

The database language of OODBS is akin to the object-oriented
programming language such as Smalltalk or C++. You can enjoy the full
versatility of these general purpose programming language in writing
application programs with the database language.

As apparent from these, OODBSs, in general, are for programmers who
write application programs which serve end users' needs. MOOD, on the
other hands, is not; it is for end users. It is provided with a user
interface named the object editor or OE in short. With OE, we can;

  (1) Edit class definition objects and save them. This replaces the
      data definition language.

  (2) Edit data objects and save them.

  (3) Create query objects, let the system select data objects which
      match the queries, and browse them.

In the other words, we can do everything necessary to manage and use
database with OE. MOOD, therefore, needs no programming language and,
in fact, has none. In this regard, MOOD may better be categorized to
the OODBS application.

The architecture of MOOD as such is the consequence of the nature of
information to be dealt with in material database. If we describe the
nature with a single word, "variety" will be the one most appropriate.
No fixed data structure can handle a handful of material data because
their contents differ from one to another. The feature of OODBS
relevant here is not the intimacy with programming languages but the
flexibility of data structure which allows us to construct data
objects with a variety of structures which match the variety in the
information to be dealt with. Upon inputting and retrieving data
objects, end users are forced to face this variety in data structure
since significant information is born in the structures of individual
representations.

Yet, we say that MOOD is a general purpose OODBS. This is not in the
sense that we can develop application programs on it, but in the
sense that it generally supports the essential capabilities of OODBS;

  (1) The abstract data type.

  (2) The nesting of structured data objects.

  (3) The class hierarchy.

  (4) The inheritance of attributes along the hierarchy.

  (5) Matching between objects along their structures with the
      knowledge of the class hierarchy.

For additional features of MOOD4, please consult its manual available
with the program. Although they are biased to the processing of
material data (or, more generally, scientific and technical data),
MOOD with these capabilities can be used in any application domain at
least by the stage where you are to examine how well the pieces of
information of interest are represented in OODBS and how well specific
items of interest are discriminated out from the database as such.

Questions and suggestions on this software which are ever welcome
indeed may be addressed to;

     Noboru Ono
     Dept. of Machine Intelligence and Systems Engineering,
     Faculty of Engineering, Tohoku University.
     Tel:++22-216-8111,
     Fax:++22-216-8156,
     E-mail:[e-mail]



> OBST/STONE (Forschungszentrum Informatik [FZI], Karlsruhe, Germany)

Version: OBST3-3.5
Date:    2/2/94

The OBject system of STONE --- OBST
-----------------------------------

The persistent object management system OBST was developed by
Forschungszentrum Informatik (FZI) as a contribution to the STONE
project (supported by grant no. ITS8902A7 from the BMFT, i.e. the
German Ministry for Research).

OBST was originally designed to serve as the common persistent
object store for the tools of an software engineering environment.


Data Model
---------

The OBST data model can be characterized by the following properties:

 * Schema definition language syntactically similar to C++
 * Support of multiple inheritance
 * Generic classes
 * Abstract classes and methods
 * Distinction between public, protected, and private methods
 * Redefinition of methods
 * Overloading of methods

Schemas and Containers
----------------------

Schemas are compiled by the OBST schema compiler. The compilation
results are instances of classes of the meta schema. From these
instances in a next step interfaces to different programming languages
can be generated. At present the C++ language binding is implemented.

Objects are stored in so-called containers. The container an object
belongs to is determined at the time of object creation and fixed
throughout the object's lifetime. Containers are the units of
clustering, synchronization, and recovery. Objects can be referenced
by other objects across container boundaries.

Incremental Loading
-------------------

OBST provides a mechanism to incrementally load methods. This enables
programs to deal with objects whose type is defined after the program
itself has been developed. This is useful in systems that provide for
inheritance and it supports schema evolution. We used it e.g. for
programs that interpret the object base and call methods of the
found objects (for example the below mentioned browser).

Prototype
---------

Since end 1990 the first prototype of OBST is available and is shipped
to interested universities and research institutions. The current
version is publicly available via FTP (see below) since March '92.
There is a mailing list (see below) with >>100 subscribers.

The system comes with the schema compiler, a library of predefined
classes (like Set<Entity>, List<Entity>, String, ...), a graphical
object browser (more a shell than a browser), the structurer and
flattener (STF), tclOBST, and all manuals. For STF and
tclOBST see below.

Structurer and Flattener
------------------------

This is a tool to build objects from bytestrings and flatten objects
down to bytestrings. It is intended to be used when coupling UNIX
tools to the object management system. The user defines a grammar that
describes her objects. Afterwards, the structurer parses an ascii
text according to the given grammar and creates an OBST object
structure that represents the corresponding parse tree.
The flattener does the inverse transformation, that means it generates
an ascii text from a given OBST object structure according to the given
grammar.

tclOBST
-------

tclOBST is a library which provides an embedding of OBST into the
interactive tool command language tcl, developed by John Ousterhout
at the University of Berkeley.
Based on the standard tcl shells, which are also comprised in the
tclOBST distribution, tclOBST offers interactive access to the complete
functionality modelled by OBST schemata.


System Requirements
-------------------

For the prototype's installation a C++ compiler
(GNU g++ 2.3.3/2.4.5/2.5.7 or AT&T 2.0/2.1/3.01) and the
X-Windows system (currently X11R4 or X11R5) for the graphical tools
are required.
Installation is well-tried on SUN Sparc stations and should be no
problem on other UNIX machines, too. You can find a more detailed
description of the supported platforms in the README.install.OBST*.

--------------------------------------------------------------------

For more information please mail to:

                Forschungszentrum Informatik (FZI)
                       OBST Projekt
                 Haid-und-Neu-Strasse 10-14
                     D-76131 Karlsruhe
                          Germany

or email to:  [e-mail]

Phone:        ++49-721-9654-601
Fax:          ++49-721-9654-609
Teletex:      721 190 fziKA

The OBST system is available via anonymous FTP from
ftp.fzi.de [141.21.4.3].

The system as well as some overview papers, documentation
(User's Guide, Language Reference Manual, Tutorial, ...),
and lots of manual pages can be found in the directory /pub/OBST.

There are mailing lists for announcing OBST enhancements,
new versions, porting hints, etc. as well as for exchanging experiences
with other OBST users.

Send a mail with content 'LONGINDEX' to [e-mail] to learn about
the mailing lists which are currently installed:
    echo LONGINDEX | mail [e-mail]

The mailing lists are maintained by an automatic list processor.
Use 'HELP' to learn about the commands understood by this processor:
    echo HELP | mail [e-mail]

Bug reports should contain a small example program with which the
bug can be reproduced, or at least a detailed description of the
observed phenomenon. They should also mention:
     o OBST version
     o configuration parameters for your OBST version
       (from file config.status)
     o kind and version of C++ compiler
     o machine
     o operating system

Besides bug reports we are strongly interested in all experiences
our users make with OBST (e.g. sufficiency of data model, performance,
...) and in our users' application areas and the applications as
well. So, please don't hesitate to send us a short note.

Best regards and happy OBST programming.

   The OBST Team,

    Boris Boesler, Dirk Eichberg, Frank Fock, Axel Freyberg,
    Michael Gravenhorst, Ingolf Mertens, Michael Pergande, Christian Popp,
    Bernhard Schiefer, Dietmar Theobald, Axel Uhl, Walter Zimmer

---

BTW "Obst" is the German word for "fruit",
    so have a fruitful time with OBST!



> Ode

                                 Ode 2.0
                       An Object-Oriented Database

       C++ Compatible, Fast Queries, Complex Application Modeling,
       Multimedia Support, and more

See APPENDIX E, Databases, for description.


> Oggetto, University of Lancaster, UK.

Developed at the University of Lancaster, UK.  Summary NYI.

"Oggetto: An Object Oriented Database Layered on a Triple Store",
J.A. Mariani, The Computer Journal, V35, No 2, pp108-118, April 1992.


> ORION (Now marketed as ITASCA)

ORION was a prototype OODBMS developed at MCC, an American consortium by Won
Kim and his group.  Won Kim has left MCC and formed a new company, UniSQL, in
Austin, with a new product of the same name.

See also entry under "ITASCA".

REFERENCES:

I have found nearly a dozen papers published by the ORION folks.
Overviews at various stages in its development and commercialization
can be found in:

[KBGW91] Won Kim, N. Ballou, J.F. Garza, and D.; Woelk. A
         distributed object-oriented database system supporting
         shared and private databases. ACM Transactions on
         Information Systems, 9(1):31--51, January 1991.

[KGBW90] W. Kim, J.F. Garza, N. Ballou, and D. Woelk.
         Architecture of the orion next-generation database
         system. IEEE Transactions on Knowledge and Data
         Engineering, 2(1):109--24, March 1990.

[KBCG89] Won Kim, Nat Ballou, Hong-Tai Chou, and Darrell Garza,
         Jorge F. Woelk. Features of the ORION object-oriented
         database system. In Won. Kim and Frederick H.
         Lochovsky, editors, Object-Oriented Concepts, Databases
         and Applications, chapter 11. Addison-Wesley, Reading,
         MA, 1989.

[KBC+88] Won Kim, N. Ballou, Hong-Tai Chou, J.F. Garza,
         D. Woelk, and J. Banerjee. Integrating an
         object-oriented programming system with a database
         system. In Proceedings of the ACM Conference on
         Objected-Oriented Programming:  Systems, Languages and
         Applications (OOPSLA), pages 142--152, San Diego, CA,
         September 1988. Published as ACM SIGPLAN Notices
         23(11).
         [Pointers to the previous papers documenting each of the
          advanced features listed above are cited therein.]


The paper most relevant to the issue of schema evolution is the
following:

[BKKK87] J. Banerjee, W. Kim, H-J. Kim, and H.F. Korth.
         Semantics and implementation of schema evolution in
         object-oriented databases. In U. Dayal and I. Traiger,
         editors, Proceedings of the SIGMOD International
         Conference on Management of Data, San Francisco, CA,
         May 1987.


You might also like to look at Kim's book, which provides a good
introduction to OODBMS, while focusing on the ORION work:

[Kim90]  Won Kim. Introduction to Object-Oriented Databases.
         Computer Systems. MIT Press, Cambridge, MA, 1990.


> OTGen (Carnegie Mellon University/UMass Amherst)

OTGen is a design for a system to support schema evolution in
object-oriented databases.  The chief contribution of OTGen is support
for programmer extensibility of transformation functions to allow a
system to support a wide range of schema changes, not just those that
can be easily automated.  While OTGen was never implemented, it is
based on the implementation of TransformGen, a system to support the
evolution of the specialized databases used by Gandalf programming
environments.  For more information on OTGen and TransformGen, please
see:

Barbara Staudt Lerner and A. Nico Habermann, "Beyond Schema Evolution
    to Database Reorganization", in Proceedings of the Joint ACM
    OOPSLA/ECOOP '90 Conference on Object-Oriented Programming:
    Systems, Languages, and Applications, Ottawa, Canada, October
    1990, 67-76.

Barbara Staudt, Charles Krueger, and David Garlan, TransformGen:
    Automating the Maintenance of Structure-Oriented Environments,
    Computer Science Department Carnegie-Mellon University, Technical
    Report CMU-CS-88-186, November 1988.

David Garlan, Charles W. Krueger, and Barbara J. Staudt, "A Structural
    Approach to the Maintenance of Structure-Oriented Environments",
    in Proceedings of the ACM SIGSOFT/SIGPLAN Software Engineering
    Symposium on Practical Software Development Environments, Palo
    Alto, California, December 1986, 160-170.

Contact:
Barbara Lerner
[e-mail]


> VODAK

Research in the framework of VODAK focuses on an extensible data
model and database programming language, an advanced transaction
model, object-oriented query language, and support for multimedia data.

The VODAK Data Model Language VML

Usually database models lack mechanisms for extending them with
additional modeling primitives. This limitation does not allow the
adaptation of the models for specific application needs, e.g. database
integration, multimedia document handling, hypertext modeling, etc.

The VODAK Model Language VML  homogeneously integrates the concept of
metaclasses and the separation of types and classes with other
object-oriented concepts such as properties, methods, inheritance, and
object identity. Complex nested data structures can be defined using
the set, array, tuple, and dictionary type constructors. VML supports
its own programming language for implementing methods, specifying
transactions and an ad hoc query language.

In VML classes are used to organize a set of objects corresponding to
real world entities and relationships between them. Object types define
the structure of objects and the operations defined on these
structures.  They are associated with classes in order to determine the
structure and behavior of the class' instances. Metaclasses are first
class objects whose instances are classes. Metaclasses are associated
with three object types: an (optional) own-type extending their own
behavior, an instance-type specifying the behavior of their instances
(which are classes), and an  instance-instance-type specifying the
behavior of the instances of their instances.  Metaclasses can be
organized in an instantiation hierarchy of arbitrary depth.

This approach leads to an open, adaptable data model which provides for
the specification of additional modeling primitives at a meta layer of
the database schema. The concept of metaclasses and the separation of
classes and types allow to determine the structure and behavior of
objects and the individual inheritance behavior via semantic
relationships between arbitrary objects already at the meta layer
independently from the specifications given at the application layer
for the application specific classes.


The VODAK Transaction Model

In VODAK, we focus on two specific problems of transaction management.

1. Operations to read and edit (hyper)documents are typically complex,
interactive and of long duration. A high degree of concurrency is
required to reduce the number and length of times a transaction is
blocked.

2. A publication environment has to handle existing database systems
for using and modifying remote information and documents.  Transaction
managers of existing systems, i.e. concurrency control and recovery,
have to be integrated in a transparent way utilizing the functionality
of existing managers.

Our transaction model is based on open nested transactions. Compared to
conventional flat transactions, nested transactions allow more
concurrency and are more flexible for recovery.  A nested transaction
is a tree-like structure, dynamically built up by the call of
subtransactions until a bottom implementation level is encountered.

We extended the open nested model from a fixed calling hierarchy of
operations in a layered system (multi-level transactions) to an
arbitrary calling hierarchy of operations in an object-oriented system.
Commutativity of operations is applied to system defined VODAK methods,
and to methods of user defined object types.  For the second type of
operations, we developed a framework to specify commutativity and
inverse operations in VML.

Query Processing

Although nearly all object-oriented data models proposed so far include
behavioral aspects, most object-oriented query languages, algebras and
query optimization strategies simply adapt relational concepts since
they focus on the complex structures of objects and neglect the
behavior. We claim that this approach is not sufficient since it does
not reflect the much richer semantics methods can carry which have to
be taken into account for really efficient query processing. The quite
straightforward approach we consider is to integrate methods in an
algebraic framework for query processing and to make there partial
knowledge about methods available in the form of equivalences. We
integrate algebraic set operators with methods defined in database
schemas within an object-oriented data model. We investigate the impact
on the architecture of the query processor when the algebra becomes an
extendible component in query processing.

Multimedia Support

The V3 Video Server was built as a demonstration showing a multimedia
application developed on top of the VODAK database management system.
The V3 Video Server allows a user to interactively store, retrieve,
manipulate, and present analog and short digital video clips. A video
clip consists of a sequence of pictures and corresponding sound.
Several attributes like author, title, and a set of keywords are
annotated.

In the future, the VODAK DBMS will be enhanced with new built-in
functionality for multimedia datatypes. Therefore, existing components
of VODAK must be changed and new ones must be added to support time
dependencies, high data volumes, and user interaction.

Query Processing

Although nearly all object-oriented data models proposed so far include
behavioral aspects, most object-oriented query languages, algebras and
query optimization strategies simply adapt relational concepts since
they focus on the complex structures of objects and neglect the
behavior. We claim that this approach is not sufficient since it does
not reflect the much richer semantics methods can carry which have to
be taken into account for really efficient query processing. The quite
straightforward approach we consider is to integrate methods in an
algebraic framework for query processing and to make there partial
knowledge about methods available in the form of equivalences. We
integrate algebraic set operators with methods defined in database
schemas within an object-oriented data model. We investigate the impact
on the architecture of the query processor when the algebra becomes an
extendible component in query processing.

The VODAK Prototype

The system architecture consists of a central database environment and
several external database environments to which the user wants to have
integrated access. Each of these environments consists of an object
manager, a message handler, a transaction manager, and a communication
manager. In addition to these components an external database
environment includes a database interface module which realizes the
access to an external database system.

The DBMS components are currently built on top of DAMOKLES and will be
in the near future on top of ObjectStore.

A first version of a C++ based prototype of VODAK is available for Sun
Sparc Stations under certain conditions.  It implements all the
features specified in including e.g. metaclasses, transactions, and
remote message execution.

References

P. Muth, T. Rakow, W. Klas, E. Neuhold:  A Transaction Model for an
Open Publication Environment.  A. K. Elmagarmid (Ed.): Database
Transaction Models for Advanced Applications. Morgan Kaufmann
Publishers, San Mateo, Calif., 1992.

Wolfgang Klas, Karl Aberer, Erich Neuhold Object-Oriented Modeling for
Hypermedia Systems using the VODAK Modeling Language (VML) to appear
in: Object-Oriented Database Management  Systems, NATO ASI Series,
Springer Verlag Berlin Heidelberg, August 1993.

Karl Aberer, Gisela Fischer Object-Oriented Query Processing: The
Impact of Methods on Language, Architecture and Optimization
Arbeitspapiere der GMD No. 763, Sankt Augustin, July 1993.

T.C. Rakow, P. Muth The V3 Video Server: Managing Analog and Digital
Video Clips, Sigmod 93, Washington, DC.

For further information contact

{aberer,muth,rakow,klas}@darmstadt.gmd.de

  GMD-IPSI
  Dolivostr. 15
  D-64293 Darmstadt
  GERMANY

  FAX: [phone]


Commercial Systems
__________________

> ArtBASE  (Object-Oriented Data Model)

by:     ArtInAppleS Ltd.
        Kremelska 13
        845 03 Bratislava
        SLOVAKIA
        Phone: x42-7-362-889
        fax:   x42-7-777 779
        EMail: [e-mail]

Distributor for Germany:
        ARS NOVA Software GmbH
        Stettener Strasse 32/3
        73732 Esslingen a.N.
        Germany
        Phone: x49-711 3704001
        Fax:   x49-711 3704001
        EMail: [e-mail]

Languages: Objectworks\Smalltalk by ParcPlace Systems, Inc.

Platforms: Unix, PC Windows, Macintosh

Features:
- Fully implemented in Objectworks\Smalltalk
  (ArtBASE is delivered with source code)

- ArtBASE extents Smalltalk of persistency. Persistent objects are handled the
  same way as transient objects.

- Optimistic and pessimistic concurrency control.

- Transactions, including long lived transactions

- User concept with access restrictions

- storing of classes and methods in the database - entire applications
  may be stored in an ArtBASE database, including the data AND the
  application classes

- Currently, a single user version is available. The Distributed Multi User Server Version
  will be presented at the OOPSLA'93 at Washington D.C. in September 1993 for Unix
  environments and PCs.

- Existing applications can be turned to database applications very easily using ArtBASE


> EasyDB (Objective Systems, Sweden)

EasyDB features a (programming language independent) Data Definition
Language (DDL) for the definition of schemas.  It relies on the
Entity-Attribute-Relationship model.  Data Manipulation Languages
(DML) include a Navigational Query language (NQL) embedded in a host
language (C available now, Ada in January '93), and a generic C++
class library.

On Schema Evolution (from original survey):
The schema may be freely extended with new items (types, domains,
attributes, entities, relationships etc.). Deletion of items is not
allowed.

Data created with an older schema may co-exist with newer data. Old
applications need not be recompiled when the schema is updated.
Attempts by newer applications to access `older' data in an
inconsistent way are detected and reported via an exception handling
system.

[Tomas Lundstrom <[e-mail]>]

Objective Systems SF AB (Ericsson)
Box 1128
S-164 22 Kista, Sweden
tel : [phone]
fax : [phone]
contact: Jaan Habma, [e-mail]


> GemStone (Servio)

First introduced in 1987, Servio's GemStone is the oldest commercial ODBMS
available today. GemStone is particularly well suited for use in complex
multi-user, multi-platform client/server applications. It supports
concurrent access from multiple external languages, including Smalltalk-80,
Smalltalk/V, C++ and C. GemStone also provides a dialect of Smalltalk as an
internal DML, which can execute methods or entire applications in the
database.

Servio also offers GeODE (GemStone Object Development Environment), an
object database application development environment which allows developers
to build complete object applications visually, without writing code. With
GeODE's visual programming tools, programming an application is a matter of
wiring together graphical representations of encapsulated code blocks. A
simple extension mechanism promotes the re-use of code, thereby increasing
the speed of program development. Also, association of application user
interface elements with database objects is established through simple
graphical tools. GeODE applications are stored and run in the GemStone
database, and so are both self-porting and network-aware, and can be
accessed externally from any of the GemStone language interfaces. Because
of GemStone's network architecture, Geode applications can operate easily
in a client/server environment.


 ==============================================================================

GEMSTONE

GemStone is a highly scalable client-multiserver database for commercial
applications. GemStone's features include:

o  Active Database -- GemStone allows database application developers to
   write methods which are stored and executed directly in the database.
   These methods can be accessed either internally, or from external client
   applications. This can significantly reduce network traffic and allow
   applications to take advantage of the superior compute power of the
   server. This also eliminates the need to rebuild and re-deploy
   applications whenever application or business processing rules change.
   This in turn allows for centralized code development and management,
   architecture-independent code that ports itself to new platforms,
   reduced network usage, and true client/server applications that share
   compute load between client and server machines.

o  Concurrent Support for Multiple Languages -- GemStone provides
   concurrent support for applications developed in Smalltalk, C++, C or
   GeODE. All applications, regardless of language, can have simultaneous
   access to the same database objects.

o  Flexible multi-user transaction control -- Multiple users can
   operate in the database simultaneously, with a variety of transaction
   control modes available.

o  Object-level security -- Authorization control can be applied to any
   object in the database, allowing for fine tuning of object security.

o  Dynamic schema and object evolution -- GemStone supports schema
   modification through class versioning and allows full migration of
   objects between versions of their classes with a simple message send.
   Migration is fully customizable and is undoable.

o  Production Services -- GemStone delivers the full suite of features
   required in any production-ready networked database including online
   backup, rapid recovery, referential integrity, sophisticated concurrency
   control, and event signals and notifiers.

o  Scalability -- In a recent independent benchmark, GemStone scaled to
   support more than 1,000 simultaneous log-ins and 100 concurrent active
   users on a mid-sized SMP server.

o  Legacy Gateways -- GemStone incorporates gateways or data bridges
   that allow object applications to integrate legacy data, whether in SQL,
   IMS, VASM or other formats. The level of integration between GemStone
   and legacy data and applications can range from simple query access to
   extensive read-write interoperability.


 ==============================================================================

GEODE

GeODE is a comprehensive environment for rapidly designing, building and
deploying production-quality commercial object applications. Its design
promotes code reuse in a team programming environment for increased
productivity. GeODE consists of six main elements:

o  Visual Application Manager -- Provides centralized management
   of each application and its component parts, and a namespace for
   addressing known objects.

o  Visual Schema Designer -- Allows the development of database schema
   visually, making the process more interactive and intuitive than with
   object-oriented programming languages. It also provides analysis tools
   for examining an existing schema.

o  Visual Forms Designer -- The Forms Designer reads GemStone class
   definitions and an associated data dictionary to automatically create
   default forms suitable for simple data entry. These forms can be rapidly
   customized, using a wide selection of user interface components and
   field types, which include image and sound support, and a large set of
   form design aids. The list of field types can be extended interactively.

o  Visual Program Designer -- The Visual Program Designer allows developers
   to visually create and modify the behavior of an application without
   having to write code. Programs are created by connecting visual program
   blocks to field blocks drawn from the forms created in the Forms
   Designer. A large collection of predefined program blocks is provided
   with GeODE, and users can extend the catalog in any of a number of
   simple ways. Code-based programming can be integrated routinely.

o  Developer Class Library - GeODE comes standard with more than 480
   classes and thousands of methods, and is easily extended for handling
   specialized applications. In a team environment, some programmers can
   develop visual applications while others write new methods that are
   encapsulated into visual program blocks for easy reuse.

o  Developer Tools -- GeODE includes tools for debugging, browsing and
   inspecting applications. Included in this set of tools are several
   debuggers, browsers, inspectors, an object clipboard, an image editor,
   and a code profiler for performance analysis.


 ==============================================================================

PLATFORMS

GemStone release 3.2 and GeODE 2.0 and all language interfaces are
available for UNIX workstations and servers from SUN, HP, IBM, Sequent, and
DEC. Client-only support is available in a number of languages for Windows
3.1, OS/2 and Macintosh. Servio is an active member in the Object
Management Group and the ANSI Smalltalk standardization committee. Servio
supports SUN ODMG, ANSI C++ and intends to comply fully with the emerging
standards.

 ==============================================================================

REFERENCES

  [Maier, et al. 84] D. Maier, J. Stein, A. Otis, A. Purdy, ``Development
  of an object-oriented DBMS'' Report CS/E-86-005, Oregon Graduate Center,
  April 86 - ACM 0-89791-204-7/86/0900-0472

  R.G.G. Cattell: Object Data Management - Object-Oriented and Extended
  Relational Database Systems; Addison-Wesley. ISBN 0-201-53092-9

  Robert Bretl, David Maier, Allen Otis, Jason Penney, Bruce Schuchardt,
  Jacob Stein, E. Harold Williams, Monty Williams. "The GemStone Data
  Management System." Chapter 12 of "Object-Oriented Concepts, Databases
  and Applications", by Kim and Lochovsky.


 ==============================================================================

CONTACTS

 === Headquarters - San Jose ====

Servio Corporation
2085 Hamilton Avenue
Suite 200
San Jose  CA  95125

Tel: [phone]
Tel: [phone]
Fax: [phone]

 === Chicago ====

Servio Corporation
8410 Bryn Mawr
Suite 400
Chicago  IL  60631

Tel: [phone]
Fax: [phone]

 ===  New York ====

Servio Corporation
1120 Avenue of the Americas
4th Floor
New York  NY  10036

Tel: [phone]
Fax: [phone]

 === Dallas ====

Servio Corporation
14875 Preston Road
Suite 550
Dallas  TX  75240

Tel: [phone]
Fax: [phone]

 === Europe/UK ====

Servio UK
Criterion House
Beauchamp Court, Victors Way
Barnet  EN5 5TZ  England

Tel: [phone]
Fax: [phone]

 === Japan ====

Servio Corporation
Daito-Eiwa Building, 7F
5-11 Nihonbashi-Hakozakicho
Chuo-ku  Tokyo 103  Japan

Tel: [phone]
Fax: [phone]

 =====================
 === Distributors ====
 =====================

 === Germany, Austria, Switzerland ====

ObjectOriented System Technologies
Baroper Str. 337
Dortmund  50  W-4600
Germany

Tel: [phone]
Fax: [phone]

 === Japan ====

Japan Information Processing Service Co., Ltd.
2-4-2 Toyo , Koto-ku
Tokyo, 135, JAPAN

Tel: [phone]
Fax: [phone]

--------------------

Nexus Technology K.K.
Suite 901
Botan 3-11-1
Koto-ku  Tokyo 135  Japan

Tel: [phone]
Fax: [phone]

 === Taiwan ====

Anco Technologies
11-1F, 76 Tun Hwa S. Road, Sec. 2
Taipei
Taiwan, R.O.C.

 === Italy ====

Etnoteam S.P.A.
Via Adelaide Bono Cairoli 34
Milano  20127  Italy

Tel: [phone]
Fax: [phone]

 === England ====

AI International Ltd.
1 Parkview Road
Berkhamsted
Herts  HP4 2EY  England

Tel: [phone]
Fax: [phone]

 ==== Mexico ====

TEIX, Sistemas de Informacion
Estrategica S.A. de C.V.
Antonio M. Anza No. 43
Col Roma  Mexico D.F.  06700

Tel: [phone]


> ITASCA
                       ITASCA ODBMS V2.2

                      Itasca Systems, Inc.
                       7850 Metro Parkway
                      Minneapolis, MN 55425
                        [e-mail]
                         [phone]

                          Sandy Miezwa
                         [phone]

Introduction

Itasca Systems develops, markets, and supports ITASCA, a distributed
active object database management system and related tools. The initial
research work for ITASCA occurred in the Object-Oriented and Distributed
Systems Lab at the Microelectronics and Computer Technology
Corporation (MCC) in Austin, Texas. The research was known as the
ORION prototypes.

The ITASCA Distributed ODBMS is a language neutral, full-featured, active
object database that supports data access from various object
languages. ITASCA allows clients to transparently access data that is
distributed among multiple servers.  ITASCA supports full dynamic schema
modification that can be performed during any phase of the software
lifecycle.  Applications written in dissimilar and incompatible languages,
such as C++ and CLOS, share objects through ITASCA. ITASCA stores methods
inside the database, promoting reusability and maintainability.  The only
commercial ODBMS based upon the MCC Orion technology, ITASCA is considered
by many to be the most feature-rich ODBMS on the market today.

This overview describes release 2.2 of the ITASCA Distributed Object
Database Management System. It describes how ITASCA functions,
outlines its implementation features, and explains some of the system
benefits.


History of ITASCA

ITASCA is based on a series of object database research prototypes. Work
on these prototypes began in 1985 at the Microelectronics and Computer
Technology Corporation (MCC) Object-Oriented and Distributed Systems
Laboratory. MCC released the first prototype, ORION-1, in May, 1987, as
a single-user system. MCC extended ORION-1 to the ORION-1SX
prototype system and released it to the shareholder companies in April,
1988. ORION-1SX was a multi-user system with a multi-client, single
server architecture. The third prototype, ORION-2, introduced a distributed,
object-oriented architecture for a multi-user environment. MCC released
the third prototype to shareholder companies in July, 1989. ORION-2 has a
multi-client, multi-server architecture. Having met its objectives, MCC
stopped all work on ORION at that time. Over five million dollars was spent
for the three generations of prototypes.

The ITASCA product is an extension and commercialization of the ORION-2
prototype from MCC. Itasca Systems has added major enhancements and
features, improved the performance, and strengthened the code. It now runs
on UNIX systems from multiple vendors. ITASCA is an industrial-strength,
documented product, fully supported by Itasca Systems, Inc. Itasca Systems
continues to develop tools and other products to work with ITASCA.


Overview

ITASCA employs a distributed architecture with private and shared objects
spread across UNIX-based computers on a local-area network. The
ITASCA model follows the object-oriented view that uniformly models any
real-world entity as an object. Each object has a unique identifier along with
a state and behavior. Attributes represent the state of an object. Methods
(code) define the behavior of an object. A class object collects objects that
share the same set of attributes and methods. Subclasses derive from
existing classes. The resulting schema, or database definition, is a class
hierarchy. Each subclass inherits all the attributes and methods of its
superclasses. ITASCA supports multiple inheritance. A subclass may derive
from more than one superclass.

One of the breakthroughs of object-oriented technology is the reusability of
code. ITASCA allows for the active management of both reusable code and
data in an integrated system. Developers may write applications in C++,
CLOS, C or Common Lisp. This means ITASCA is language neutral. Objects
stored using one programming language can be accessed by other
programming languages. It also means an application program need not be
written in an object-oriented language.

The ITASCA database management system has features belonging to most any
database system. This includes persistent storage for data and schema,
concurrency control and locking, transaction management, multiple
security levels, and logging and recovery for both CPU and disk media
failure. Additional features of ITASCA include dynamic schema
modification, long-duration transactions, shared and private databases,
distributed version control, distributed transaction management, distributed
query management, distributed change notification, object migration, and
an extensible architecture.

Shared and private databases exist in a distributed environment in ITASCA.
The shared database is distributed across workstations (sites) in a network.
An ITASCA server controls the partition of the shared database at each site.
ITASCA clients provide transparent access to the various partitions of the
shared database. The architecture allows any number of private databases at
each distributed database site. Data can move between private and shared
databases. Private databases allow private data that is not shared with other
users of the database.

ITASCA stores the schema redundantly at each site to improve
performance. The schema storage also includes code in the form of
methods. Management of schema updates is automatic for all sites. This
includes sites that were off-line during any changes. Automatic distribution
of schema changes, including method code changes, simplifies database
administration.

ITASCA stores each instance of data in one site. The system or a user may
move the data from one site to another to improve data locality. Access to
moved data remains transparent. There is no need for a user or application
to know the specificlocation of data in the ITASCA distributed database.
ITASCA will automatically find the location of the data. This simplifies
distributed application development. The developer can rely on ITASCA
finding data in the distributed database.

No single site acts as a master site, thus ITASCA's architecture has no
single point of failure. ITASCA has neither a central data server nor a
central name server. This is important for maintaining a database system
with high availability in a networked workstation environment.

ITASCA supports dynamic schema modification to create a flexible
environment for changing or customizing a database system. Authorized
users can add and remove attributes or change the subclass/superclass
relationship at any time. Authorized users can also add or remove partitions
of the shared database at any time. All this can be done interactively without
affecting other parts of the ITASCA database at the time changes occur to
the schema. There is no need to "bring the system down" or off-load/reload
data to restructure the database. Dynamic schema modification can
significantly reduce maintenance costs. It also is useful in environments
where change to data definitions are normal or relatively frequent.

ITASCA has a sophisticated security authorization technique tied to the
class hierarchy. It supports both positive and negative authorizations at any
level in the class hierarchy. For example, granting access to all objects but
one requires only two authorizations: a global grant followed by a specific
denial. Authorization extends to classes, instances of classes, attributes,
and methods. Also, inheritance of authorization reduces the work of database
administration.

Long-duration transactions allow users to check objects out of the shared,
distributed database into their private databases. Users can then change the
objects in the private databases without affecting the shared database or
other users. These changes can be committed to the private database. Then,
at any later time, the user can check the updated object or objects back into
the shared database.

ITASCA supports version control of objects. A new version of an object
promotes the original or parent object to restrict further changes to the
parent. ITASCA also supports alternate versions such that multiple versions
can have the same parent. Promoting an object version to a released status
restricts any deletion of the object. ITASCA uses generic versions to
dynamically reference the most recent or default version of an object
without any intervention by a user or application.

Change notification in ITASCA is either flag-based or message-based.
Flag-based notification will identify an updated object upon querying the
object for such information. It is a passive notification scheme. Message-
based notification, on the other hand, is an active notification scheme. It
will execute a method (or code) upon an update or other change to an object.
Such methods can send mail messages or invoke other methods or
programs.

Memory management in ITASCA uses both page and object buffers.
ITASCA has a traditional database page buffer scheme that contains pages
with multiple objects. Desired objects move from the page buffer to an
object buffer. The object buffer then provides ITASCA with enhanced in-
memory performance because it contains only frequently-referenced
objects.


> Matisse

OODBMS FEATURES LIST:

An Industrial Strength Open Semantic Object Database

Performance
-       Symmetric, Fine Grain, Multi-Threaded Architecture
-       Parallel and Asynchronous Disk I/O
-       Automatic Disk Optimization through Dynamic Clustering
-       High Speed OLTP Environment
Reliability
-       24 Hour - Mission Critical Operation
-       Media Fault Tolerant (Object Replication)
-       Transparent On-line Recovery