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Chapter 27
Object-Oriented DBMSs - Standards
and Systems
Transparencies
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Chapter 27 - Objectives
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Object Management Group (OMG), CORBA,
and other OMG standards.
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Main features of ODMG Object Standard:
–
Object model
–
Object Definition Language (ODL)
–
Object Query Language (OQL)
–
Language bindings.
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Main features of ObjectStore:
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Architecture
–
Data Definition
–
Data Manipulation.
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Object Management Group (OMG)
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International non profit-making consortium
founded in 1989 to address object standards.
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Several hundred member organizations
including many platform and major software
vendors.
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Primary aims of OMG are:
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Promotion of object-oriented approach.
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Development of standards in which location,
environment, language, and other characteristics
of objects are transparent.
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Not recognized standards group but aims to
develop de facto standards.
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Object Management Architecture
Four areas identified for reference model:
Object Model (OM) - Design-portable abstract model
for communicating with OMG-compliant object-
oriented systems.
Object Request Broker (ORB) - Handle distribution
of messages between application objects in a highly
interoperable manner.
Like distributed ‘software bus’ enabling objects to

make/receive requests/responses from a provider.
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Object Management Architecture
Object Services - Provide main functions for
realizing basic object functionality. Many of
these services are database-oriented.
Common Facilities - Comprise a set of tasks that
many applications must perform but are
traditionally duplicated within each one.
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Object Reference Model
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Object Model
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Common Object Request Broker Architecture
(CORBA)
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Defines architecture of ORB-based environments.
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Basis of any OMG component, defining parts that
form ORB and associated structures.
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Some elements of CORBA are:
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Interface Definition Language (IDL).
–

Type model.
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Interface Repository.
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Methods for getting interfaces/specifications of
objects.
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Provides static and dynamic mechanism for clients
to issue request to objects.
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CORBA ORB Architecture
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Other OMG Specifications
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UML provides common language for describing
software models.
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Meta-Object Facility (MOF), defines common,
abstract language for specification of
metamodels.
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XML Metadata Interchange (XMI) maps MOF to
XML. XMI defines how XML tags are used to
represent MOF-compliant models in XML.
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Common Warehouse Metamodel (CWM) defines
metamodel representing both business and
technical metadata commonly found in data

warehousing and business intelligence domains.
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CWM Sub-Metamodels
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CWM Relational Data Metamodel
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Model-Driven Architecture (MDA)
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OMG hoped OMA would be common OO
middleware standard. However:
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Microsoft produced DCOM (Distributed Common
Object Model),
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Sun developed Java, which came with its own
ORB, Remote Method Invocation (RMI),
–
another set of middleware standards emerged with
XML and SOAP (Simple Object Access Protocol).
◆
Also e-Business increased pressure on
companies to integrate their corporate databases.
Enterprise Application Integration (EAI) is one
of current key challenges for companies and,
rather than helping, middleware may be part of
problem.
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Model-Driven Architecture (MDA)
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MDA is an approach to system specification and
interoperability building upon 4 specifications
discussed above.
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Based on premise that systems should be
specified independent of all hardware and
software details.
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Thus, while software and hardware may change
over time, the specification will still be
applicable.
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MDA addresses complete system lifecycle from
analysis and design to implementation, testing,
component assembly, and deployment.
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Model-Driven Architecture (MDA)
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To create an MDA-based application, a
Platform Independent Model (PIM) is produced
that represents only business functionality and
behavior.
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PIM can then be mapped to one or more
Platform Specific Models (PSMs) to target
platforms like CORBA Component Model

(CCM), Enterprise JavaBeans (EJB), or
Microsoft Transaction Server (MTS).
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Both the PIM and the PSM are expressed using
the UML.
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MDA covers full range of pervasive services
already specified by OMG, such as Persistence,
Transactions, and Security.
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Model-Driven Architecture (MDA)
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Object Data Management Group
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Established by vendors of OODBMSs to define
standards.
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Have produced an Object Model that specifies
a standard model for the semantics of database
objects.
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Design of class libraries and applications
using these semantics should be portable
across various OODBMSs.
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Object Data Management Group
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Between release 2.0 (1997) and 3.0 (late 1999),
ODMG expanded its charter to cover the
specification of universal object storage
standards.
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At same time, ODMG changed its name from
Object Database Management Group to Object
Data Management Group to reflect expansion of
its efforts beyond merely setting storage
standards for object databases.
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The Java binding was submitted to JCP as basis
for Java Data Objects (JDO).
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In 2001, ODMG completed its work and
disbanded.
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Object Data Management Group
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Under its extended charter, ODMG specification
covers both OODBMSs that store objects directly
and Object-to-Database Mappings (ODMs) that
convert and store the objects in a relational or
other database system representation.
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Both types of products are referred to generically
as Object Data Management Systems (ODMSs).
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ODMSs make database objects appear as

programming language objects in one or more
existing OOPLs, and extend programming language
with transparently persistent data, concurrency
control, recovery, associative queries, and other
database capabilities.
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Object Data Management Group
◆
Major components of ODMG architecture for
an OODBMS are:
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Object Model (OM).
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Object Definition Language (ODL).
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Object Query Language (OQL).
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C++, Smalltalk, and Java Language Binding.
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ODMG OM - Basic Modeling Primitives
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Basic modeling primitives are object/literal.
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Only an object has a unique identifier.
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Objects/literals can be categorized into types.
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All objects of given type exhibit common

behavior and state. A type is itself an object.
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Behavior defined by set of operations that can
be performed on or by object.
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State defined by values objects carry for a set
of properties.
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ODMG OM - Basic Modeling Primitives
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Property may be either an attribute of object or
relationship between object and one or more
other objects.
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ODMS stores objects, enabling them to be
shared by multiple users and applications.
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ODMS based on a schema defined in ODL.
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ODMG Object Model - Objects
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Object types decomposed as atomic,
collections, or structured types.
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Structured types as defined in ISO SQL
standard.
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Objects created using new() of corresponding

factory interface provided by language
binding.
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Each object has a unique identity, the object
identifier, which does not change and is not
reused when the object is deleted.
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May be given one or more names by user.
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Set of Built-in Types for ODMG Object Model
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ODL Interface for Objects
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