// Load modules
?- [students>>stud],
    [faculty>>advisor],
	[temporal>>time].

?- Method[mustDefine(on)]@\sys.

// Queries
?S[valid(?Semester)] :-
	?S:student[joined->?Join, graduated->?Grad]@stud,
	?Semester[sameOrBefore->?Grad, sameOrAfter->?Join]@time.

?S[advisor(?Semester) -> ?A] :-
	?S:student[advisor->?A[since->?Since, until->?Until]]@stud,
	?Semester[sameOrBefore->?Until, sameOrAfter->?Since]@time.

?S[status(?Semester) -> ?StatName] :-
	?S[status->?_Stat[type->?StatName, since->?Since, until->?Until]]@stud,
	?Semester[sameOrAfter->?Since, sameOrBefore->?Until]@time.

// For a given semester, write down all the currently valid MS students
// along with their advisors.
// Will use, say, Spring 2004.
?- ?Sem=spring(2004),
    // Note: the following are defined in the current module, not stud
    ?_S[valid(?Sem), status(?Sem)->ms, advisor(?Sem) -> ?[?_AdvInfo]@stud],
    ?_S[name->?N]@stud,
    ?_AdvInfo[name->?AdvisorName]@advisor.