3.1.4 Functional model

The CORBA functional model is divided in three layers. Due to the object-oriented nature of the OMG framework, services contained in the upper layers are able to inherit functionality from underlying layers.

1.

CORBAservices ([12]) form the lowest layer in the functional model and are mandatory for the operation of any CORBA-based implementation. The Externalization, Properties, Change Management and Licensing services are examples of CORBAservices particularly useful for management purposes.

2.

The next building blocks in the hierarchy are CORBAfacilities; they consist of multi-purpose services useful for a large part of applications. Typical kinds of CORBAfacilities are: Information Management, Task Management and Systems Management. The latter provides the basis for introducing management functionality into the OMG framework and is of big interest for the definition of delegatable functionality as described in section 4 of this paper.

3.

Domain Interfaces, finally, are high-level services suitable for specific application domains. As systems management is an important issue in all kinds of application domains, this layer does not define any management functionality. Instead, it is inherited from the underlying CORBAservices and CORBAfacilities.

Application objects reside on top of the three layers and obtain an important part of their functionality by inheriting from the three layers below. A typical example for an application object is a distributed management application.