[This is preliminary documentation and subject to change.]
In addition to class-specific properties, Web-Based Enterprise Management (WBEM) defines a set of system properties that are associated with all classes and instances of classes. System properties provide information that is applicable to every class, such as its name, its derivation, and its namespace.
As with system classes, system properties begin with a double underscore to differentiate them from properties created by applications or providers, which cannot start with a single or double underscore. Another way to identify a system property is by using the IWbemClassObject::Get method.
Not all system properties are available on all classes or instances at all times. For detailed information about each of the WBEM system properties and their availability, see the System Properties reference.