Distributed Technology - Distributed Operating Systems - Lecture Slides, Slides of Computer Science

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CORBA

Distributed Technology

CASE STUDY

Most popular distributed object technologies

• OMG’s CORBA (Common Object Request Broker Architecture).
• Microsoft’s DCOM (Distributed Component Object Model).
• Sun’s Java/MRI (Java/Remote Method Invocation).

OMG

• The Object Management Group (OMG), is an open membership, not-for-profit consortium that produces and maintains computer industry specifications for interoperable enterprise applications.
• The OMG was created in 1989 and has about 700 hundred members in the Organization:

OMG (cont.)

• Some of OMG Actual Members:
  • Sun Microsystems
  • GE Transportation
  • Motorola (Platform)
  • NASA (Government)
  • Massachusetts Institute of Technology (University)
  • Adobe Systems

CORBA SPECIFICATION (cont.)

• A syntax for describing the interfaces of objects used in the development of distributed applications. IDL (Interface Definition Language).

CORBA APPLICATIONS

• Telephone Networks worldwide
• Banking Application on every continent
• Manufacturing
• Government
• Industrial
• Car dashboards to mainframes
• Controlling Telephone switches

CORBA FEATURES

• CORBA supports many existing languages. Including C, C++, Java, Smalltalk, and Ada.
• CORBA also supports mixing these languages within a single distributed application.
• CORBA supports both distribution and Object Orientation.
• CORBA is an industry standard. This creates competition among vendors and ensuresthat quality implementations exist. The use of the CORBA standard also provides the developer with a certain degree of portability between implementations.
• CORBA provides a high degree of interoperability. This insures that distributedobjects built on top of different CORBA products can communicate. Large companies do not need to mandate a single CORBA product for all development.

CORBA SERVICES

• Naming Services
• Event Service
• Notification Service
• Security Service
  • Authentication
  • Access control can be applied to CORBA objects.

CORBA ARCHITECTURE

Basic Concept

CORBA ARCHITECTURE (Cont.)

ARCHITECTURE (cont.)

• CORBA IDL stubs and skeletons:

S erve as the “glue” between the client and server applications, respectively, and the ORB.

ARCHITECTURE (Cont.)

• Dynamic Invocation Interface (DII): This interface allows a client to directly access the underlying request mechanisms provided by an ORB. Applications use the DII to dynamically issue requests to objects without requiring IDL interface-specific stubs to be linked in.
• Dynamic Skeleton Interface (DSI): This is the server side's analogue to the client side's DII. The DSI allows an ORB to deliver requests to an object implementation that does not have compile-time knowledge of the type of the object it is implementing.
• Object Adapter: Allows the interaction between the ORB with the objects.

Steps for creating a CORBA

1. Define the remote interface (IDL) Primitive Data types: long , short, unsigned short, long, unsigned long, float (IEEE), double, char, boolean, octet, any. Extended built in data types: long long (64 bits), unsigned long long, long double, wstring, fixed. Complex Types: struct, union, enum, muti-dim. arrays

• Example: : FileInterface.idl

interface FileInterface { typedef sequence Data; Data downloadFile(in string fileName); };

Steps for creating a CORBA (cont.)

2. Compile the remote interface (IDL)

The IDL Compiler implements language mapping in software. After checking the IDL code for errors, the compiler will produce the following files: prompt> idlj –fserver FileInterface.idl (-fclient or –fall)

• Server skeletons for each IDL interface
• Client stubs for each IDL interface
• The program (Java or C++) interfaces
• A Java / C++ class for IDL defined struct
• Helper classes for each IDL defined type