CORBA Services are services that
are essential for implementing objects. The CORBA Services that have
been specified thus far by OMG include: A Concurrency Control Service that protects the integrity of
an
object’s data when multiple requests to the object are processed concurrently. An Event Service
that
supports the notification of interested parties when program-defined events occur.
An Externalization Service that
supports the conversion of object state to a form that can be transmitted
between systems by a means other than a request broker.
Life Cycle Services that support
creation, copying, moving, and destruction of objects.
A Naming Service that permits object
references to be retrieved through associations between names and
objects, and for those associations to be created and destroyed.
A Persistent Object Service that
supports the persistence of an object’s state when the object is not active
in memory and between application executions.
A Query Service that supports operations
on sets and collections of objects that have a predicate-based,
declarative specification and may result in sets or collections of objects.
A Relationship Service that provides
for creating, deleting, navigating, and managing relationships between
objects (for example, a containment relationship between a ā€˛folder“ object and the ā€˛document“
objects that
are considered to be ā€˛in“ that folder).
A Transaction Service that provides
support for ensuring that a computation consisting of one or more
operations on one or more objects satisfies the requirements of atomicity (if a transaction is interrupted
by a
failure, any partially completed results are undone), isolation (transactions are allowed to execute
concurrently, but the results are the same as if they executed serially), and durability (if a transaction
completes successfully, the results of its operations are never lost, except in the event of catastrophe).
CORBA Services that are in the
process of being specified and are expected to be completed in 1995 include:
A Licensing Service that will control
and manage remuneration of suppliers for services rendered.
A Property Service that will support
the association of arbitrary named values (the dynamic equivalent of
attributes) with an object.
A Security Service that will support
authentication, authorization, integrity, and privacy to degrees, and
using mechanisms, that are yet to be determined.
A Time Service that will provide
synchronized clocks to all objects, regardless of their locations.
CORBA Services that are not yet
in the process of being specified include:
A Change Management Service that
would support the identification and consistent evolution of
configurations of objects.
A Collection Service that would
support the creation and manipulation of collections of objects.
A Data Interchange Service that
would support the exchange of data between objects.
A Replication Service that would
provide for the explicit replication of objects in a distributed environment
(for the purpose of availability or fault tolerance) and for the management of consistency of replicated
copies.
A Trader Service that would provide
a matchmaking service between clients seeking services and objects
offering services.
1.Introduction
