sentence(X) :- X=[cntower,is,a,tower].
sentence(X) :- X=[a,house,is,a,building].
sentence(X) :- X=[a,tower,is,a,structure].
sentence(X) :- X=[a,building,is,a,structure].

%%sentence(X) :- X=[a,follows,b].
%%sentence(X,W) :- X=[a|Y],Y=[follows|Z],Z=[b|W].
%%sentence(X,W) :- =([a|Y],X),=([follows|Z],Y),=([b|W],Z).

sentence --> [a],[follows],[b].
xsentence(Q) --> [a],[follows],[b],{Q=great}.
xsentence(Q) --> [a],[follows],[c],{Q=good}.

xxsentence(Q,P) --> [a],[follows],letter(T),{Q=good,P=T}.
letter(T) --> [a],{T=a}.
letter(T) --> [b],{T=b}.
letter(T) --> [c],{T=c}.


factoid(C) --> person(P),[is],property(T),{C=..[T,P]}.
person(peter) --> [peter].
person(mary) --> [mary].
person(john) --> [john].
property(tall) --> [tall].
property(smart) --> [smart].
property(smart) --> [clever].
property(smart) --> [intelligent].

%% a Sth1 is a Sth2 to be: sth2(X) :- sth1(X)
%% sth1 is a Sth2 to be: sth1(sth2).
  
taxonomy(C) --> article,[Sth1],{not(Sth1=ghost)},[is],article,[Sth2],{H=..[Sth2,X],B=..[Sth1,X],C= :-(H,B)}.
taxonomy(C) --> [Sth1],[is],article,niceone(Sth2),{C=..[Sth2,Sth1]}.
article --> [a].
article --> [an].
article --> [the].

niceone(person) --> [person].
niceone(car) --> [car].
niceone(car) --> [automobile].