HP WBEM Services Software Developer's Kit for HP-UX Provider and Client Developer's Guide A.01

Schema Design and Implementation
Schema Design
Chapter 334
Note that associations and aggregations inherit. That is, if a superclass
has an association to another class x, all subclasses also inherit an
association relationship to x. Also, it is possible to create specialized
subclasses of the association if required (for example to define additional
properties or methods).
Next consider ancillary objects that should be associated with the
primary managed elements. These include entities such as services,
settings, and statistics. Services and services access points (SAP) are
ways of representing services and the availability of those services as
supported by managed element. A service class provides methods for
enabling and disabling those services. Settings represent managed
elements operational parameters. Several settings can be associated
with an entity. Statistics represent statistical information or metrics
related to a managed element. Each of these ancillary object classes
should be associated with a managed element with appropriate
cardinalities.
Next, consider what diagnostics and indications may be associated
with a managed element. Diagnostics, as modeled using the Common
Diagnostics Model (CDM), enable one to represent the diagnostic test
itself (including status, characteristics,and methods to start and stop the
diagnostic test), settings for the diagnostic, and results of previously run
diagnostic tests.
Finally, in some cases it may be useful for a client to be able to
communicate with the provider itself (as opposed to the resources for
which it acts as a gateway), treating the provider as a resource to be
managed. This may be the case if the provider has "side effects": state or
resources of its own that affect its operation. Examples of such resources
could include configuration information (of the provider itself), logging
behavior (stopping, starting), databases, communication facilities, and
other features.
When such a need exists, it is not appropriate to model the provider's
own resources in the classes it serves. These classes must be reserved for
the management of the underlying platform resources. Instead, it is
appropriate to define a new class by extending CIM_Service and/or
related areas of the CIM model (it is permissible to define a class at the
root level of the hierarchy, but this is not generally recommended). This
class can define local properties or methods as necessary. The provider
being managed should be the provider for this class of object, as well as
for the classes representing the resources that it instruments.