ISA Operator for Schema Queries
The ISA operator is a WQL-specific operator that can be used in data, event, and schema queries.
When ISA is included in the WHERE clause of an schema query, it requests that the query be applied to all subclasses of the class you specify.
For example, the following statement requests notification every 10 minutes of instance modification events for all instances that are members of any class deriving from the Win32_LogicalDisk class.
SELECT * FROM __InstanceModificationEvent WITHIN 600 WHERE TargetInstance ISA "Win32_LogicalDisk"
The following query returns the definition for the CIM_Processor class and definitions for all of its subclasses.
The class meta_class identifies this as a schema query, the property called __this identifies the target class of the query, and the ISA operator requests definitions for the subclasses of the target class.