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ORB Services are invoked implicitly in the course of application-level interactions. ORB Services range from fundamental mechanisms
such as reference resolution and message encoding to advanced features such as support for security, transactions, or replication.
An ORB Service is often related to a particular transparency. For example, message encoding – the marshaling and unmarshaling
of the components of a request into and out of message buffers – provides transparency of the representation of the request.
Similarly, reference resolution supports location transparency. Some transparencies, such as security, are supported by a
combination of ORB Services and Object Services while others, such as replication, may involve interactions between ORB Services
themselves.
ORB Services differ from Object Services in that they are positioned below the application and are invoked transparently to
the application code. However, many ORB Services include components which correspond to conventional Object Services in that
they are invoked explicitly by the application.
Security is an example of service with both ORB Service and normal Object Service components, the ORB components being those
associated with transparently authenticating messages and controlling access to objects while the necessary administration
and management functions resemble conventional Object Services.