A property serves to define a relationship of a specific kind between two classes. The property is characterized by an intension, which is conveyed by a scope note. A property plays a role analogous to a grammatical verb, in that it must be defined with reference to both its domain and range, which are analogous to the subject and object in grammar (unlike classes, which can be defined independently). [...] Properties may themselves have properties that relate to other classes (This feature is used in this model only in order to describe dynamic subtyping of properties). Properties can also be specialized in the same manner as classes, resulting in IsA relationships between subproperties and their superproperties. In some contexts, the terms attribute, reference, link, role or slot are used synonymously with property.