In BMC Server Automation, a hierarchical group of user-defined property classes and subclasses. You can assign properties to each class and subclass. A subclass inherits all of the properties of its parent class. Using inheritance, you can create complex property structures built from custom classes and subclasses. You can then create multiple instances of these property structures. For each instance, you can set individual properties to particular values. You can assign an instance of a custom property class to a system object by using a property from a property class.