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CORBA Common Object Request Broker Architecture OMG - “Object Management Group” OMG, a group of about 500 organisations (see www.omg.org) promotes standards for inter-operation of object-oriented systems, across boundaries of Operating Systems, Networks, Programming languages.
Common Object Request Broker Architecture
OMG - “Object Management Group”
OMG, a group of about 500 organisations (see www.omg.org) promotes standards for inter-operation of object-oriented systems,
across boundaries of
RMI - Remote Method Invocation
ORB - Object Request Broker
OQL - Object Query Language
ODMG - Object Data Management Group
ODMG-93 = -1.0; ODMG-2.0 standards
OMA - Object Management Architecture
ODL - Object Definition Language
IDL - Interface Definition Language
GIOP - General Inter- ORB Protocol
IIOP - Internet Inter- ORB Protocol
DII - Dynamic Invocation Interface
DSI - Dynamic Skeleton Interface
BOA - Basic Object Adapter
But automated stub generation, from object interface definitions, does simplify programming. It can be done
• by extending an existing HLL, or
• by using a platform-independent language-independent IDL, with compilers producing stubs for all languages and all platforms.
OMG promotes CORBA, which defines
The CORBA IDL has elements
• a header file, for use by implementations of client & server objects
• a stub, for use by client object
• an object-definition skeleton, needing to be turned into an object implementation by further programmer effort.
Stubs provide static methods that can be invoked by a client object, these methods will communicate transparently with the local ORB.
That local ORB will if necessary find a remote server ORB (possible because objects "register" their identity and their interface with an ORB, using its Interface Repository).
The server ORB invokes the methods of the server object, and provides other services to it (eg registering, timeouts) via an "object adapter".
an OO Database Adapter standard is also proposed.
Interface Repository API provides DII (Dynamic Invocation Interface) ability - with which a client object may dynamically discover objects & their methods, and invoke those methods, using metadata.
Server ORB uses DSI (Dynamic Skeleton Interface) ability for dynamic objects with no static skeleton.
• CORBAservices - system-level services for standardising the lifecycle of objects: such as object naming, object creation, object relocation, controlling access to objects
• CORBAfacilities - higher-level services - categorised as
Some CORBAservices - eg concurrency control, query services - overlap with desired features of a DBMS.
There would be prohibitive overhead if each ODBMS object were individually registered with ORB, hence the desirability of a specialised alternative to BOA, the Object Database Adapter, for flexibility and performance. ORB may handle access to unregistered objects maintained within ODBMS by invoking methods of the ODBMS.