This is a complex version of the
examples/Papers/1998/RichtersAndGogolla example
with simple invariants to ensure object diagrams
which make sense and pre-/postconditions
for every operation with side effects.

CarRental2.use:
more classes and associations than the simple example
there is a 3-ary association

many attributes (with primitive and complex types)
there are queries and operations changing the system
state

CarRental2.cmd:
creates a state with at least
one object per class and assigned attribute values
not all constraints evaluate to true
there are inconsistent invariants

CarRental2.olt: