CORBA (Common Object Request Broker Architechture)

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CORBA (Common Object Request Broker Architechture)

• Aniket Prabhune
• Varun Saini
• Balaprasuna Chennupati
• Lally Singh

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CORBA

• Day1
• Aniket Introduction, OMA, ORB Core, OMG IDL,
  IDL Stubs and Skeletons
• Varun Interface Repository, Dynamic Invocation
  and Dispatch (DII, DSI)
• Day2
• Prasuna Object Adapters, Inter-ORB protocols
  (IIOP/GIOP), Services (Event, Naming, Trading,
  Transaction)
• Lally COM vs CORBA, QoS, Examples and
  Applications

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CORBA

• Heterogeneous and Open Systems
• Engineering tradeoffs
• Cost Effectiveness
• Legacy Systems
• Need for integrating diverse applications within
  Distributed heterogeneous environments

SV97
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OMG (Object Management Group)

• Formed in 1989 to develop, adopt and promote
  standards for the development and deployment of
  applications in distributed heterogeneous
  environments.
• Largest software consortium in world with 800
  developers, vendors and end users on member list
• CORBA Industry Standard for open distributed
  processing

SV97
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OMA (Object Management Architecture)

• Object Model and Reference Model
• Object Model
• Defines how objects distributed across a
  heterogeneous environment can be described
• Object is an encapsulated entity with a distinct
  immutable identity whose services can be accessed
  only through well defined interfaces
• Object References

SV97
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OMA Reference Model

• Characterizes the interactions between the
  objects
• Interface Categories in OMA Reference Model

Application Interfaces
Domain Interfaces
Object Request Broker
Object Services
ACP99
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OMA Object Frameworks

• AI

DI
OS
AI
DI
ORB
DI
AI
OS
OS
AI Application Interface
OS Object Service
DI Domain Interface
ORB Object Request Broker
ACP99
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Features of CORBA

• ORB Core
• OMG Interface Definition Language
• Language Mappings
• Stubs and Skeletons
• Interface Repository
• Dynamic Invocation and Dispatch
• Object Adapters
• Inter-ORB protocols
• Services

SV97
9
Relation between features
Client Application
Server Application
Static Stub
Sktn
DSI
ORB Interface
ORB Interface
OA
DII
n/w
Server ORB Core
Client ORB Core
IDL Dependant
Multiple OAs
Same for all applications
ACP99
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ORB Core

• Deliver request to target object
• Return response to the clients
• Transparent Client/Object Communication
• Object Location
• Object implementation
• Object Execution State
• Object communication mechanism

SV97
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IDL (Interface Definition Language)

• Interfaces are defined in the OMG IDL
• Language-Independent declarative language
• eg
• // OMG IDL
• interface Factory
• Object create()

SV97
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IDL

• Includes
• Built-in Types long, short, float, double, char,
  boolean, octet, enum, etc
• Constructed Types struct, union
• Template Types string, sequence, fixed point
  decimal
• Interface Inheritance Open-Closed Principle
• Object Interface

SV97
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Language Mappings

• Determines how the OMG IDL features are mapped to
  the facilities of a given programming language
• e.g.

OMG IDL Type C Mapping
long, short long, short
float,double float,double
boolean bool
char char
struct struct
union class
sequence class
.... ....
SV97
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Stubs and Skeletons

• IDL interface
• Stub Compiler
• Stubs (Client Side) Skeletons (Server
  Side)
• Fixed for a given language and interface
• Hide the ORB from application programmer

NE95
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Marshalling Unmarshalling

• eg Acct -gt List()

program language request
buffer
client
stub
client ORB
marshalling
n/w
buffer
target object
skeleton
server ORB
operation invocation
unmarshalling
SV97 NE95
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Design Patterns (Stubs and Skeletons)

• Connect programming Language world to the
  underlying ORB transparently
• Stub adapts function call style of its language
  mapping to the request invocation mechanism of
  the ORB
• Skeleton adapts request dispatching mechanism of
  the ORB to the upcall method form expected by the
  object implementation
• Form of Adapter and Proxy patterns
• Proxy Provide a surrogate or placeholder for
  another object to control access to it
• Adapter Convert the interface of class to
  another interface clients expect

SV97
DP95
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References

• SV97 Vinoski, S., CORBA Integrating
  Diverse
• Applications Within
  Distributed
• Heterogeneous Environments
  IEEE Communications Magazine, Vol. 35, No.
  2, February 1997
• NE95 Edwards, N., CORBA An Industrial
  Approach to
• Open Distributed Computing
• ACP99 Henning, M., Vinoski, S., Advanced
  CORBA
• Programming with C, Addison Wesley, 1999.
• DP95 Gamma Erich., Helm Richard, Johnson
  Ralph, Vlissides, John, Design Patterns
  Elements of Reusable Object-Oriented
  Software,Addison Wesley, 1995.