Final answer:
The incorrect statement about a UML class is that it is a set of objects. It is instead a classification that defines common properties and behaviors of multiple objects and can show multiplicity in relationships, but is not a collective set by itself.
Step-by-step explanation:
The statement about a UML class that is NOT true is: It is a set of objects. A UML (Unified Modeling Language) class is indeed a classification of objects, meaning it defines the common properties and behaviors of a group of objects. It is quite similar to a data entity in that respect, encapsulating data and functionalities that the objects or instances of the class have in common. The notion of multiplicity refers to the relationship between objects, typically how many instances of a class can relate to instances of another class, and this concept itself does not directly pertain to the definition of a class