Each theater shows several movies and charges the same ticket price for every movie. Observe that the shownAt relationship of Movie and the nowShowing relationship of Theater are declared to be inverses of each other. Theater also has a method numshowing() that can be applied to a theater object to nd the number of movies being shown at that theater.
ODL also allows us to specify inheritance hierarchies, as the following class denition illustrates:
An object of class SpecialShow is an object of class Movie, with some additional properties.