HP WBEM Services for HP-UX and Linux System Administrator's Guide

How Resources are Represented (CIM Schema)
Appendix A92
The class is the basic modeling unit. It is a collection or set of objects
that have similar properties and purposes. Each class defines a certain
type of managed object, for example operating systems or system
memory. Objects in the class contain properties (describing what it is)
and methods (what it can do). A class can contain other classes (its
subclasses). It can also contain instances.
Subclasses are grouped by similarities. Subclasses inherit properties
and methods from their parent (their superclass), and can also add their
own local properties and methods. Subclasses are themselves classes,
and they can have their own subclasses.
CIM_SoftwareElement, for example, is a class. It has several subclasses,
like HPUX_SoftwareElement, Win32_SoftwareElement
Linux_RPM_SoftwareElement, Linux_Debian_SoftwareElement.
An instance can be a discrete occurrence of any object, like your
computer’s hard drive or the printer on your desk. It is the most specific
member of the hierarchy. An instance cannot have any subclasses. All
instances in a class share the same properties and methods. Each has a
unique name (see key properties, below).
Methods are the behaviors of the class, for example, the
OperatingSystem class has a Reboot method and a printer has an
EnableDevice method to put it online. Not all classes have methods.
An intrinsic method models a CIM operation. Standard intrinsic
methods (such as enumerateInstances, getInstance, modifyInstance) are
relevant to all classes.
An extrinsic method is defined on a CIM Class in some Schema that is
unique to that class.
Properties are the attributes of a class. For example, there is a
ParticipatingCS association between a CIM_ComputerSystem and a
CIM_Cluster. This association has two properties, RoleOfNode and
StateOfNode, to describe attributes of the ComputerSystem as a node
within the Cluster.
Key properties (one or more properties defined with a “key” qualifier)
are identifiers. Keys in classes and subclasses provide a way to uniquely
identify the instance that inherits them. All instances inherit a key, or a
set of keys, from their superclass. The value that the instance gives these
keys is its own identification. It is the only instance in its namespace
that is allowed to have that “name.” More than one key property is a
compound key.