CORBA (Common Object Request Broker Architecture)

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CORBA(Common Object Request Broker Architecture)

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Current problems in computing

• customers do not want to create one monolithic
  application
• e.g., one large C program
• want to break up the job into several
  sub-problems and create (or implement) solutions
  for each sub-problem separately
• easier to concentrate on while developing the
  solutions and also easier to modify a solution
• these solutions will work correctly only if they
  are built on standard interfaces
• failure to create such a standard interface is
  known as interoperability problem

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Three levels of interoperability

• lowest level
• through emails and file transfers
• each site has its own platform, method and file
  structure but the communication is through simple
  stream of text
• middle level
• web browsing
• scan through documents in other sites but agreed
  upon a common language such as HTML
• upper level
• programs in different sites interacting with each
  other
• may be written in different languages and run on
  different platforms
• how is this possible? through CORBA

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CORBA solution

• provides a common infrastructure through which
  objects at different sites communicate with each
  other
• classes that create objects are not part of the
  infrastructure and they reside in the same site
  where the objects reside
• both classes and objects need to be in the same
  site because
• objects do not carry method definitions with
  them these are available in the classes
• classes do not communicate with each other only
  objects communicate with each other

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Network protocol between Object A and CORBA
Interface of A
Object A
CORBA
Interface of B
Network protocol between Object B and CORBA
Object B
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CORBA solution to Interoperability

• each object declares its interface in a format
  known to the CORBA infrastructure
• every message sent from a sender to a receiver is
  converted into a standard format at the junction
  between the objects interface and CORBA
  infrastructure
• The CORBA infrastructure maintains the format,
  the list of clients (senders and receivers), and
  any information that needs to be transparent to
  clients such as
• clients identifications
• clients interfaces

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Object handles

• each client object has a unique identifier known
  as a handle
• this is not (necessarily) an address such as URL
• it can be in any format as designated by the
  CORBA infrastructure
• advantage when the object moves from one
  location to another (happens often), the handle
  also moves with it and so the other objects do
  not need to worry about the physical location of
  the object
• CORBA infrastructure is the only one who need to
  be informed about the physical location of an
  object

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What is required on part of CORBA?

• a standard environment that provides the basic
  services
• transactions between objects including formats
  for message communication
• security
• event-handling
• persistence
• objects must stay forever cant disappear as
  soon as a transaction is performed
• a software distribution technology to enable a
  multi-platform software marketplace
• the CORBA Component Model (CCM) provides these
  two facilities

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OMA The application integrator of CORBA

• basic CORBA infrastructure only connects objects
  together, and not the applications
• CORBA infrastructure does not know anything about
  the applications for which the objects are
  created, and does not know anything about the
  applications in which these objects can be used
• solution There is an architecture called OMA
  (Object Management Architecture) that takes care
  of mapping between objects and applications

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Application Objects
CORBA facilities
Vertical CORBA facilities
Manufacturing
Telecom
E-Commerce
Transportation


Business Objects
HealthCare
Finance/Insurance
Life Science
More
Horizontal CORBA facilities

Internationalization
Time
Agent facility
More
Object Request Brokers
Naming, Trader
Events, Notification
Transactions
Security
Persistent State
Property
More
CORBA services
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CORBA services

• provide the services that any object needs to
  communicate through the CORBA infrastructure
• unique naming for objects and methods
• event handling
• for the basic execution paradigm
• persistent state
• To store the objects forever
• transaction manager
• To handle transaction issues such as implementing
  protocols
• security handler
• more

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CORBA services (continued)

• lowest level communication primitives
• includes
• OLTP (OnLine Transaction Processing) for business
  applications
• an object trader service (a kind of yellow pages)

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CORBA facilities

• provide services that are common for several
  applications
• example PIDS (patient identifier services) is an
  application package that provides services to
  health care services all health care
  applications will use the common format to
  identify patients
• each kind of applications has its own CORBA
  facilities package
• see the diagram for the OMA

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Horizontal and Vertical facilities

• vertical CORBA facilities are packages that are
  common to a small subset of applications
• Health care, E-Commerce, Insurance
• horizontal CORBA facilities are packages that are
  common to several (a fairly large set of)
  applications
• print facilities, timing, international
  standards,
• together, these two facilities provide packages
  that are common for almost every application
• application objects simply write the client code
  to use these facilities

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Benefits of CORBA

• developers can make use of all platforms and
  languages that they bought/use
• because CORBA virtually provides an interface for
  every platform and language, including
  traditional languages such as COBOL and Ada
  although these languages seem to disappear
• no need to change a platform or a language for a
  different application
• tools and software that were developed and are
  running on these platforms will continue to use
  CORBA facilities and services

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Benefits of CORBA (continued)

• maximizes programmers productivity
• programmers need to write only the application
  code that makes use of CORBA objects
• they simply use the standard interface to
  communicate with CORBA infrastructure
• learning requirement CORBA interface format
• IDL (Interface Definition Language)
• code reuse is achieved to the maximum extent
• both the application code as well as tools can be
  declared as CORBA objects

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A brief note about OMG

• OMG stands for Object Management Group
• a consortium of companies involved in common
  computing
• over 1000 companies around the world at present
  in the consortium
• software vendors, consulting companies, product
  and tool developers, interface developers,
• OMG does not develop software it only generates
  interface specifications
• OMG meets 5 times a year to administer the
  interfaces and CORBA products

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Reference

• Jon Siegel, CORBA 3 Fundamentals and
  Programming (Second Edition), John Wiley Sons,
  2000, ISBN 0-471-29518-3
• Reaz Hoque, CORBA for Real Programmers, Morgan
  Kaufmann, 1999, ISBN 0-12-355590-6

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Glossary

• CORBA
• Common Object Request Broker Architecture
• ORB
• Object Request Broker
• OMG
• Object Management Group
• A technical consortium responsible for
  registering and maintaining CORBA objects and
  services
• OMA
• Object Management Architecture
• IDL
• Interface Definition Language

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Glossary (continued)

• CCM
• The CORBA Component Model