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CORBA an introduction

• Martin Hansson

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Agenda

• Background
• Architecture
• CORBA Services (COS)
• Pros n cons
• Questions

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Agenda

• Background
• Architecture
• CORBA Services (COS)
• Pros n cons
• Questions

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About me

• 1994 - 1999
• Royal Institute of Technology, M. Sc. Computer
  Science.
• 1999 -
• Parallel Consulting Group
• 2000
• Icon Medialab Sverige

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Prerequisites

• Familiar with OOP
• Some knowledge of distributed systems
• Some knowledge of Java
• A good mind for abbr...

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Background

• New paradigmprocedural -gt object oriented
• Remote Procedure Calls (RPCs) are not enough
• A need for a standard architecture crossing
  platform boundaries

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Background

• Object Management Group formed 1989. Today 900
  members.
• Common Object Request Broking Architecture is a
  standard specified by the OMG.

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The evolution of the CORBA standard

• CORBA 1.0, October 1991
• Interface Definition Language (IDL)
• CORBA 2.0, August 1996
• Inter-ORB working
• CORBA 2.2, February 1998
• DCOM interworking, SSL security
• CORBA 3, very soon now
• CORBAComponents
• Firewall specification
• EJB coupling

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How OMG works

• Working process
• Request for Proposals
• Task Forces
• Architecture Board
• Implementation within 18 months
• Rather fast decisions, but not problem free...

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OMG Vision

• Foster interoperability and portability for
  application integration through the use of
  object-oriented standards based on commercially
  available software

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which means something like this

• An intergalactic object bus where all objects can
  be plugged in
• Programming language/platform independence
• Real reuse of code
• Industrial use of distributed systems
• A common abstract framework (and protocols, and
  terminology, and interfaces)

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When to use CORBA

• You require an open solution
• Youre aiming to sell services as a third party
• Your target system is diverse
• You develop for a system already containing CORBA
  objects

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Agenda

• Background
• Architecture
• CORBA Services (COS)
• Pros n cons
• Demo
• Questions

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Common Object Request Broker Architecture
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Common Object Request Broker Architecture

• Also known as Object Management Architecture (OMA)

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OMA from a layered prespective
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How to use CORBA

• CORBA mainly usedas middleware

Client
Business logic
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CORBA workings
Client
Server
Object bus (ORB)
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CORBA workings
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Agenda

• Background
• Architecture
• CORBA Services (COS)
• Pros n cons
• Questions

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CORBA Services

• CORBAServices (COS)
• Used for common needs
• Built to be
• scalable
• flexible
• modular

• Examples
• Time
• Persistence
• Naming
• Transaction
• Lifecycle
• Security
• Event

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COS Naming

• Names are bound to objects
• Binds are relative to their scope
• Names within a scope are unique
• Name contexts are objects them selves, and thus,
  may have names
• Objects must not have names

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CORBA Facilities

• Commonly used frameworks not tied to a specific
  domain
• Horizontal
• Generic
• Vertical
• More application specific

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CORBA Facilities, examples
At application level these make up the
different domains

• Vertical

• Horizontal

• User interfaces
• Rendering
• Graphs, forms, etc
• Information handling
• Rule handling
• ...

• E-commerce
• Finance
• Health care
• Telecom
• Transportation
• Manufacturing
• ...

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Interface Definition Language (IDL)

• One of the corner stones of CORBA
• The services are defined in IDL
• Defines interfaces and data structures
• Is not a complete programming language
• Lacks for example iterators and flow control

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IDL Characteristics

• A small example

• Errors are handled with exceptions
• Inheritage possible (even multiple)
• Parameters are passed by-reference (saves
  bandwith)

// Bank.idl module Bank interface Account
float balance() interface
AccountManager Account open(in string
name)
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The steps involved
Client code
IDL
Client
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Agenda

• Background
• Architecture
• CORBA Services (COS)
• Pros n cons
• Questions

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Pros and cons

• Pros ()
• Language independant
• Easy distribution
• Very scalable
• Platform independant

• Cons (-)
• Different vendors have different service calls
• Difficult to change ORB
• Complex

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CORBA 3 in Process

• Last parts will be released late 1999
• CORBA Components
• Better portability
• Firewall penetration
• Interoperable Naming Service
• well-known ports (IIOP 683, IIOP/SSL 684)
• Asynchronous messaging
• Objects-by-value

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Further Information

• Object Management Group
• www.omg.com
• Vendors
• www.inprise.com
• www.iona.com
• www.objectspace.com
• CORBA FAQ
• www.aurora-tech.com/corba-faq