1. Objektorienteret Middleware (OOMI)
CORBA Introduction

2. Outline CORBA (part one) Introduction & Background Architecture
Session & Presentation layer
GIOP / IIOP / CDR
CORBA Interface Definition Language – IDL
Language mappings
CORBA development steps

3. Who is the OMG? OMG: Object Management Group
Non-profit organization in the US, representatives in United Kingdom, Germany, Japan, India, and Australia
Founded April 1989
More than 800 members
Dedicated to creating and popularizing object-oriented industry standards for application integration, e.g.
CORBA 1.0 (1995) –> CORBA (2006)
UML 1.1 nov > 2.1 (2006)

4. Goal of CORBA CORBA: Common Object Request Broker Architecture
Support distributed and heterogeneous object request in a way transparent to users and application programmers
Facilitate the integration of new components with legacy components
Open standard that can be used free of charge
Based on wide industry consensus
But not much Microsoft support
Problem with CORBA
Considered too complex by many

5. The specifications CORBA is a collection of specifications
Common Object Request Broker Architecture (CORBA/IIOP) (3.0.3)
CORBA Component Model (3.0)
Light Weight CCM
CORBA/e (replaces Minimum CORBA)
Minimum CORBA (1.0)
Real-Time CORBA (Dynamic Scheduling) (2.0)
Real-Time CORBA (Static Scheduling) (1.1)
Families of specifications:
CORBAservices Specifications
CORBAfacilities Specifications
OMG Domain Specifications
IDL / Language Mapping Specifications
Many others
Realted to UML
UML Profile for CORBA (1.0)

6. Object Management Architecture (OMA)
Application Objects
Domain Interfaces
CORBA Facilities
Object Request Broker
CORBA Services (mandatory)

7. CORBA Architecture1 Many different vendors and ORB types
Many of which do not interoperate
Must check specification
OrbBacus from IONA produces both C++ and Java
Sun J2SE SDK has only Java-based ORB
C++ ORB from IONA will work with SUN ORB as specified
Many others
MicoORB, Middcor, TAO, openORB, VisiBroker

8. CORBA Architecture 2 Client Object Implementation ORB Core
Dynamic
Invocation
Client
Stubs
ORB
Interface
Implementation
Skeletons
Object
Adapter
One standardised interface
One interface per object operation
ORB-dependent interface
One interface per object adapter

9. Interoperability Protocols
Applications
Environment Specific ..
CORBA 2.0
GIOP
ESIOP
IIOP
DOETalk
DCE-CIOP
Mandatory: provides "out of the box" interoperability
IIOP: Internet Inter-ORB Protocol is the primary CORBA transport protocol

10. General Inter-ORB Protocol (GIOP)
Handles the session & presentation layer
Defines seven message primitives:
Request, Reply, Locate Request, Locate Reply, Cancel request, Close Connection, Message Error
More simple than JRMP for Java RMI
Internet Inter-ORB Protocol (IIOP)
Maps GIOP to TCP/IP
Provides operations to open and close TCP/IP connections
Is required from ORBs for CORBA compliance
But intra vendor ORB com is not restricted to this
More on the IIOP later in the course

11. Common Data Representation (CDR)
Defined as part of GIOP
Presentation layer implementation to support heterogeneity
Mapping of IDL data types to transport byte stream
Encodings of
primitive types
constructed types
interoperable object references

12. Recap - motivation for an IDL
IDL: Interface Definition Language
Components of distributed systems are written in different programming languages
Programming languages may or may not have their own object model
Object models largely vary
Differences need to be overcome in order to facilitate integration

13. Heterogeneous OO Network
“Object Wrapping of non OO application”
CORBA
Java
Client
App.1
CORBA
Cobol Database
Server
CORBA C#
Client
App.2
TCP/IP Network
CORBA
C++
Client
App.3 DB
Different ORB’s from different vendors, on different operating systems – and written in different languages = Heterogenity

14. Avoid multiple mappings
CORBA IDL & Mappings PL 6 2 5 1 4 3
IDL PL PL 1 2
Avoid multiple mappings PL PL 6 3 PL PL 5 4

15. CORBA Programming Language Bindings
Smalltalk
C++
Ada-95
IDL
Common
Object
Model C
Java
.NET
Cobol
Janeva / Middcor (C#)

16. Interface Definition Language (IDL)
Language for expressing all concepts of the middleware’s object model
Should be
programming-language independent
not computationally complete
Bindings to different programming languages are needed
language bindings are specified by CORBA
The IDL is very comprehensive – please read and experiment with it

17. Example UML to IDL mapping
Organization
#name:string
uses
+transfer(p:Player)
Club
-noOfMembers:int
-location:Address
has 1 *
coaches
1..*
Trainer
-name:string 1
+train()
works for
Player
Team
-name:string
+bookGoalies()
plays in 1
11..16
-name:string
-Number:int
+book()

18. CORBA Object Model: Types
typedef struct Address {
string street;
string postcode;
string city; };
typedef sequence<Address> AddressList;
interface Team { ... };
Constructed
types
Atomic
types
Object
type

19. CORBA Object Model: Modules
Soccer::Address
module Soccer {
typedef struct Address {
string street;
string postcode;
string city; };
module People {
string flat_number;
string country;
Modules =
namespaces
People::Address

20. CORBA Object Model: Attributes
interface Player;
typedef sequence<Player> PlayerList;
interface Trainer;
typedef sequence<Trainer> TrainerList;
interface Team {
readonly attribute string name;
attribute TrainerList coached_by;
attribute Club belongs_to;
attribute PlayerList players;
... };
Clients cannot
change value
changeable
Attribute type
Attribute name

21. CORBA Object Model: Operations
Parameter kind
interface Team {
...
void bookGoalies(in Date d);
string print(); };
Parameter list
Return types
Parameter type
Parameter name
Operation name
used in requests

22. CORBA Object Model: Exceptions
Generic Exceptions (e.g. network down, invalid object reference, out of memory)
Type-specific Exceptions
Exception name
Exception data
exception PlayerBooked{sequence<Date> free;};
interface Team {
void bookGoalies(in Date d) raises(PlayerBooked); };
Operations declare
exceptions they raise

23. CORBA Object Model: Subtypes
Implicit supertype: Object
Inherited by Club
interface Organization {
readonly attribute string name; };
interface Club : Organization {
exception NotInClub{};
readonly attribute short noOfMembers;
readonly attribute Address location;
attribute TeamList teams;
attribute TrainerList trainers;
void transfer(in Player p) raises NotInClub;
Supertype
This has only been a minimal presentation of the IDL

24. Legal Values in CORBA (Types)

25. Development Steps – CORBA vs RMI & SOAP
AXIS SOAP
Design
J2SE JDK
CORBA: IDL
Java2WSDL
Interface
Definition
SOAP: WSDL
Start with Server
Interface Coding: JAVA
RMI: JAVA interface
WSDL2JAVA
Server Stub
Generation
Client Stub
CORBA: IDL
RMI: rmic
RMI: JAVA
C++, Java …
Server
Coding
Client
C++, Java …
ORB
rmiregistry
Server
Registration

26. CORBA Client and Server Implementation
Team.idl
included in
generates
reads
IDL-Compiler
Teamcl.hh
Teamcl.cc
Teamsv.cc
Teamsv.hh
Client.cc
Server.cc
C++ Compiler, Linker
Server
C++ Compiler, Linker
Client
Next we will look into a simple CORBA programming example