%% Testing the HYPROLOG system for database view update %% %% ?- current_db, grandfather(X,jens). abducibles father/2, mother/2. father(X,Y), father(Z,Y) ==> Z=X. mother(X,Y), mother(Z,Y) ==> Z=X. grandfather(X,Z):- father(X,Y), father(Y,Z). grandfather(X,Z):- father(X,Y), mother(Y,Z). current_db:- father(peter, paul), father(paul,jens), mother(marie,jens).