% adapted from 
% www.risc.uni-linz.ac.at/education/courses/ws2005/logic-programming/slides/Chapter4.pdf

facility(Pers,Fac):- book_overdue(Pers,Book),!,
                     basic_facility(Fac).
facility(Pers,Fac):-general_facility(Fac).

basic_facility(reference).
basic_facility(enquiries).

additional_facility(borrowing).
additional_facility(inter_library_loan).

general_facility(X):-basic_facility(X).
general_facility(X):-additional_facility(X).

book_overdue('C. Watzer', book10089).
book_overdue('A. Jones', book29907).

client('C. Watzer').
client('A. Jones').
client('A. Burroughs').