Operations are functions or transformations that may be applied to or by objects in a class. All objects in a class share the same operations. The objective here is to name the operations only. They are described in more detail in the dynamic and functional models.
Examples of operations are:
| Class | Operation |
| purchase order | create, approve, suspend, release, expedite, fill, archive |
| file | create, delete, copy, rename, mail |
| automobile | purchase, service, register, deregister, insure, sell |
| complaint | register, allocate, investigate, resolve |
Methods and Polymorphism
Note that the same operation can apply to many classes. For example, both purchase orders and files are created. The behaviour of the operation is dependent on its target class. The means by which an operation is performed on a class is called a method. In the example the method used to create a file will be different to that used to create a purchase order. A principle of the object model is that an operation "knows" its class and uses the appropriate method. This phenomenon is called polymorphism.