I'm currently learning OCL and for this I'm doing some exercise and I can't figure out to code the syntax for this. The diagram is the attached one, and the exercise is:
Every year, the number of passengers that arrive to a country (país), coming from a different and european country, can't be higher than the number of passengers leaving the first country to a non-european one.
How could I code this on OCL, please?
billete - ticket
vuelo - flight
aeropuerto - airport
ciudad - city
pais - country
continente - continent