Corba Part 1

7/30/2019 Corba Part 1

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Distributed Object-Based System : CORBA

(Common Object Request Broker Architecture )


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CORBA was developed by the OMG (Object Management Group)

The Object Request Broker (ORB) forms the core of any CORBAdistributed system.

It has the following Horizontal (User & System Support) facilities

User interface

Information management

System management

Task management

It has Vertical (application support) facilities in the application

domain such as as electronic commerce, banking, manufacturing


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CORBAs Interface with Other Services

All CORBA specifications are given by means of interface

descriptions, expressed in an Interface Definition Language

(IDL).

An interface is a collection ofmethods, and objects specify

which interfaces they implement.

It provides a precise syntax for expressing methods and their

parameters.


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The GeneralArchitecture of a CORBA System.


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CORBA Architecture

ORB core

DynamicInvocation

IDLStubs

ORBInterface

Object

Adapter

Static IDL

Skeleton

Dynamic

Skeleton

Client Object Implementation

Standard Interface Per-Object Type

Generated Interface

ORB Dependent

Interface

Interface

Repository

Implementatio

Repository


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CORBA Basic Architecture

o b j e c t c l i e n tn a m i n g s e r v i c e

n a m i n g

l o o k u p

s t u b

O R B

n e t w o r k

o p e r a t i n gs y s t e m

o b j e c t

i m p l e m e n t a t i o n

s k e l e t o n

O R B

n e t w o r k

o p e r a t i n gs y s t e m

l o g i c a l d a t a f l o w

p h y s i c a l d a t a f l o w


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As a distributed objects architecture, it resembles to the RMI

architecture:

Logically an object client makes method calls todistributed objects.

An object client interfaces with a proxy a stub while

the object implantation interfaces with the server-side

proxy a skeletonCORBA is not bound to a particular programming language

and hence an interface definition language (IDL) has been

introduced. IDL is an universal language with a distinct syntax

Though the syntax of CORBA IDL resembles to Java and C++, an object defined in a CORBA IDL file can be implemented

in a large number programming languages, including C, C++,

Java, COBOL, Smalltalk, Ada, Lisp, Python, and IDL Script


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Language Independence in CORBA

For each of these languages, OMG has a standardized

mapping from CORBA IDL to the programming language A compiler can be used to process a CORBA interface to

generate the proxy files

Object clients can be written in any of the CORBA-

compatible languages.


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Cross-language, cross-vendor interoperability is achieved via

the Internet Inter-ORB Protocol, or IIOP. IIOP is a transport

protocol for distributed applications written in either IDL or

Java RMI.

To allow ORBs to be interact and operate, the OMG specified

a protocol known as the General Inter-ORB Protocol(GIOP)

GIOP protocol specification provides a general framework to

be built on top of specific transport layers

IIOP is a special case of GIOP to make use of the TCP/IP

transport layer.

Inter-ORB Protocols


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Object Bus

An ORB which adheres to the specifications of the IIOP may

interoperate with any other IIOP-compliant ORBs over the

Internet. This gives rise to the term object bus, where the

Internet is seen as a bus that interconnects CORBA objects


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The IIOP specification includes the following elements:

Transport management requirements which

specifies the connection and disconnection

requirements for the object client and object server

Definition of common data representation: a coding

scheme for marshalling and un-marshalling data of

each IDL data type.

Message formats: Formats for different types ofsend/receive messages are defined. The messages allow

clients to send requests to object servers and receive

replies.


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The modelling standards belonging to the OMG include:

Unified Modelling Language (UML)

Model Driven Architecture (MDA)

Systems Modelling Language (SysML)

Business Process Modelling Notation (BPMN)

The Object Management Group (OMG) is a consortium created

to set common standards for distributed object-oriented systems

and develop enterprise integration standards for a wide range oftechnologies

OMGs middleware standards are based on the Common

Object Request Broker Architecture (CORBA)

OMG has also developed a core set of standards adapting

CORBA for embedded and real-time systems


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Object Management Architecture

Object Request Broker(ORB) component that enables clients

and objects to communicate in a distributed environment.

In CORBA, the Object Request Broker or ORB takes care of all

of the details involved in routing a request from client to object,and routing the response to its destination.

The ORB guaranteesportability and interoperability of objects

over a network of heterogeneous systems


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An Object Request Broker (ORB) provides a communication

infrastructure for invoking operations on objects

It enables to perform the operation transparently with respect to

where they are located on the network, the types of hardware and

operating system platforms on which they execute, differences indata representations between platforms, the languages in which

objects are implemented, and network transports used to

communicate with them.

CORBA specifies all of the functions that must be provided by an

ORB and a set of standard interfaces to those functions.


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OMA

(Object Management Architecture)

COMMON OBJECT SERVICES

APPLICATION OBJECTSCOMMON FACILITIES

OBJECT REQUEST BROKER

persistencenaming trading

security

HorizontalUser InterfaceMailPrinting

VerticalTelecomFinanceHealth Care


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Naming Services:An URL facilitates the localization of a resource exposed

on the Web. e.g., abc.net.in means it is likely to be an Indian

entity?A consistent and uniform naming helps processes in a

distributed system to interoperate and manage resources.

e.g., commercials use .com; non-profit organizations use .orgNaming Services are not only useful to locate resources but

also to gatheradditional information about them such as

attributes

Trading Services:Trading presents a global information repository. The global

repository can be updated by independent information

producers throughout the world-wide network, and the

information users can create effective and large information

searches.


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CORBA Facilities

CORBA Facilities are useful for constructing applications across a wide range

of application domains. They are divided into Horizontal CORBA Facilities,

which are typically more user-oriented, and Vertical CORBA Facilities, whichsupport specific application domains.

The Horizontal CORBA Facilities currently identified by OMG are grouped

into four areas:

User Interface Facilities: Desktop Management, Rendering Management,

Scripting, and User Support Facilities.

Information Management Facilities: Data Encoding and Representation, Data

Interchange, Information Exchange, Information Modeling,

Information Storage and Retrieval

System Management Facilities: Collection Management, Consistency,

Customization, Data Collection, Event Management, InstanceManagement, Policy Management, Process Launch, Quality

of Service Management, Scheduling Management, and

Security Facilities.

Task Management Facilities: Agent, Automation, Rule Management, and

Workflow Facilities.

Corba Part 1

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