| We now have a representation at two levels. The first level is the ADT level where we express everything that is done to an instance of this ADT by the invocation of defined operations. At this level, pre- and postconditions are used to describe what actually happens. In the following example, these conditions are enclosed in curly brackets.
| { Precondition: i = n where n is any Integer } i.set(1) { Postcondition: i = 1 }