A safety property is an invariant property that specifies that a particular bad behavior never happens; for example, a safety property of the turnstile problem is that the number of entries into the zoo iis never more than the number of entry fees paid. A liveness property is a property that specifies that a particular behavior eventually happens; for example, a liveness property for t!he turnstile problem is that when an entry fee is paid, the turnstile becomes unlocked. Similarly, a liveness property for the library system is that every borrow request from a Patron who has no outstanding library fines succeeds. These three properties, when expressed in logic, look like the following:
0 (nurn_coins ~ nurn_entries)
0 (insert_ coin 0 barri er=unl ocked)
D (borrow(Patron,Pub) A Patron.fines = 0) ~
03 Loan. [Loan.borrower~Patron A Loan.Publi cati on ~ Pub] )
List safety and liveness properties for your automated banking machine specification from Exercise