Slide 1 © Ingeniørhøjskolen i Århus ITONK1 CORBA & ICE Introduction

Slide 2 © Ingeniørhøjskolen i Århus Goals of this lesson After this 2x35 min. lesson you will be: Introduced to CORBA and ICE Ready to present their position in the Middleware technology family, when and where to use it You will not: Be an expert. More practice and theory is required

Slide 3 © Ingeniørhøjskolen i Århus Outline CORBA & ICE Introduction & Background Architecture Session & Presentation layer CORBA Interface Definition Language – IDL ICE IDL: Slice Language mappings

Slide 4 © Ingeniørhøjskolen i Århus CORBA Organization 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)

Slide 5 © Ingeniørhøjskolen i Århus Goal of CORBA CORBA: Common Object Request Broker Architecture Support distributed and heterogeneous object request in a way transparent to users and application programmers “King” of OO-Middleware Facilitate the integration of new components with legacy components (COBOL, C, ADA, C++, C#, Delphi, Python) Open standard that can be used free of charge Based on wide industry consensus But not much Microsoft support

Slide 6 © Ingeniørhøjskolen i Århus CORBA Problems Problem with CORBA Considered too complex by many Open standards -> cluttered solutions No Microsoft Support Is CORBA dead?

Slide 7 © Ingeniørhøjskolen i Århus 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) Real-Time CORBA (Dynamic/Static Scheduling) 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)

Slide 8 © Ingeniørhøjskolen i Århus CORBA History CORBA 1.0 (October 1991): IDL, C mapping CORBA 1.1 (February 1992): BOA CORBA 1.2 (December 1993): minor updates CORBA 2.0 (August 1996): DSI, GIOP, IIOP, C++, SmallTalk mappings CORBA 2.1 (August 1997) : Secure IIOP / SSL, COBOL, ADA mappings CORBA 2.2 (February 1998): POA, Java mapping CORBA 2.3 (June 1999): Objects by Value CORBA 2.4 (October 2000) : INS & Interop services CORBA 2.5 (September 2001) : Real-time CORBA CORBA 2.6 (December 2001) : Common Security CORBA 3.0 (July 2002): CCM, Minimum CORBA CORBA (December 2002): Minor Updates

Slide 9 © Ingeniørhøjskolen i Århus ICE Background & History ICE: Internet Communication Engine Group of ex CORBA specialists: Standard committees is ruining CORBA We need to “start-over” GPL – but controlled by one company ZeroC.com 2003: ZeroC announces ICE 1.01

Slide 10 © Ingeniørhøjskolen i Århus Application Objects CORBA Facilities CORBA Services (mandatory) Domain Interfaces Object Management Architecture (OMA) Object Request Broker

Slide 11 © Ingeniørhøjskolen i Århus CORBA Architecture1 Many different vendors and ORB types Many of which do not interoperate Must check specification compliance 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 OmniORB OrbExpress: FPGA hardware ORB!

Slide 12 © Ingeniørhøjskolen i Århus One standardised interface One interface per object operation ORB-dependent interface One interface per object adapter Dynamic Invocation Client Stubs ORB Interface Implementation Skeletons Client Object Implementation ORB Core Object Adapter CORBA Architecture 2

Slide 13 © Ingeniørhøjskolen i Århus ICE Architecture

Slide 14 © Ingeniørhøjskolen i Århus CORBA 2.0 Applications GIOP ESIOP IIOPDOETalk DCE-CIOP Mandatory: provides "out of the box" interoperability Interoperability Protocols Environment Specific.. IIOP: Internet Inter-ORB Protocol is the primary CORBA transport protocol

Slide 15 © Ingeniørhøjskolen i Århus 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

Slide 16 © Ingeniørhøjskolen i Århus 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

Slide 17 © Ingeniørhøjskolen i Århus 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

Slide 18 © Ingeniørhøjskolen i Århus Heterogeneous OO Network CORBA C++ Client App.3 CORBA C# Client App.2 CORBA Java Client App.1 TCP/IP Network CORBA Cobol Database Server DB “Object Wrapping of non OO application” Different ORB’s from different vendors, on different operating systems – and written in different languages = Heterogenity

Slide 19 © Ingeniørhøjskolen i Århus PL IDL CORBA IDL & Mappings Avoid multiple mappings

Slide 20 © Ingeniørhøjskolen i Århus IDL Common Object Model Smalltalk Cobol Java Ada-95 C++ C C CORBA Programming Language Bindings.NET Janeva / Middcor (C#) Win32 Delphi

Slide 21 © Ingeniørhøjskolen i Århus ICE Language Support C++ Java.NET Python PHP Objective C Ruby

Slide 22 © Ingeniørhøjskolen i Århus 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 – don’t try to learn everything The IDL of ICE is called SLICE

Slide 23 © Ingeniørhøjskolen i Århus Example UML to IDL mapping Player -name:string -Number:int +book() Team -name:string +bookGoalies() plays in transfer(p:Player) Club -noOfMembers:int -location:Address has 1 * uses Organization #name:string coaches 1..* Trainer -name:string 11..* +train() works for

Slide 24 © Ingeniørhøjskolen i Århus Constructed types CORBA Object Model: Types typedef struct Address { string street; string postcode; string city; }; typedef sequence AddressList; interface Team {... }; Atomic types Objec t type

Slide 25 © Ingeniørhøjskolen i Århus CORBA Object Model: Modules module Soccer { typedef struct Address { string street; string postcode; string city; }; module People { typedef struct Address { string flat_number; string street; string postcode; string city; string country; }; Modules = namespaces Soccer::Address People::Address

Slide 26 © Ingeniørhøjskolen i Århus CORBA Object Model: Attributes interface Player; typedef sequence PlayerList; interface Trainer; typedef sequence TrainerList; interface Team { readonly attribute string name; attribute TrainerList coached_by; attribute Club belongs_to; attribute PlayerList players;... }; Attribute typeAttribute name changeable Clients cannot change value

Slide 27 © Ingeniørhøjskolen i Århus CORBA Object Model: Operations interface Team {... void bookGoalies(in Date d); string print(); }; Parameter list Parameter kind Parameter type Parameter name Operation name used in requests Return types

Slide 28 © Ingeniørhøjskolen i Århus CORBA Object Model: Exceptions Generic Exceptions (e.g. network down, invalid object reference, out of memory) Type-specific Exceptions (e.g. PlayerBooked) exception PlayerBooked{sequence free;}; interface Team { void bookGoalies(in Date d) raises(PlayerBooked); }; Exception data Operations declare exceptions they raise Exception name

Slide 29 © Ingeniørhøjskolen i Århus CORBA Object Model: Subtypes 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; }; Inherited by Club Supertype Implicit supertype: Object This has only been a minimal presentation of the IDL

Slide 30 © Ingeniørhøjskolen i Århus ICE vs CORBA Comparision Performance is equal Appears easier than CORBA CORBA is based on standards and is open and widely supported ICE has ”one environment for all” – but is controlled by ZeroC ICE is GPL with all bindings Hard to find both C++, Java and.NET CORBA in one product