Our events are flying, doing actions, getting, receiving and losing. Our actions are selling, sending, telegraphing. Distinct event terms are distinct. We have two people constants, Junior and Daddy. We have among our objects Cash, a message ( ), cities, including London, Glasgow and Moscow. We also have tickets, and functions which yield destination Dest and source Source of a flight, given a ticket for that flight. We have unique names for all fluent terms, and thus for all the terms that can appear in fluents. Our fluent forming functions are At which takes a person and a place, Has which takes a persona and a thing, Happens, which takes an event, and the earlier fluents of On and Clear. Our sorts are disjoint, and the sorts of variables are to be inferred by their use.
This is equivalent to
As this is the only effect axiom for flying, we can change this to the equivalence.
This immediately gives,
as any set of preconditions is sufficient. We add the obvious axioms that describe Changes for the following effect axioms using the same method.