[This is preliminary documentation and subject to change.]
Qualifiers contain information that can be used to describe a class, an instance, a property, a method, or a parameter. Creators of classes and instances can attach qualifiers to their class and instance declarations to provide the user of those declarations, typically management applications, with more detail.
There are three categories of qualifiers: those defined by the Common Information Model (CIM), those defined by WBEM, and those defined by developers. The qualifiers defined by WBEM are known as the standard qualifiers. Some of the CIM and standard qualifiers are automatically assigned when a class or instance is created; others must be explicitly attached through inclusion in a MOF statement or a function call.
Qualifiers can be specified in class and instance declarations using the Managed Object Format (MOF) language and accessed programmatically through the IWbemQualifierSet interface. All qualifiers have a name and a value. Qualifier values can be explicit or implied. When a value is absent, the value TRUE is implied. Some qualifiers also include a descriptor known as a flavor
Depending on the qualifier and its intended use, it may or may not be required. For example, WBEM defines the Implemented qualifier for methods. If a provider defines a class with a method and includes an implementation of that method, the provider must attach the qualifier Implemented to the method declaration. Another required qualifier is the Key qualifier. The Key qualifier must be attached to every property in a class that serves as part of the key for that class. Optional qualifiers include provider-defined qualifiers and standard qualifiers that can be used as comments. A qualifier is considered optional when its removal does not affect the functionality of the class or instance with which it is associated.