% A Simple Planning Example 

initiates(X,Y) iff [
  [X=write(B), Y=in_touch_with(B)]].

precond(X,Y) iff [
  [X=write(B), Y=have_connection],
  [X=write(B), Y=know_address(B)]].

holds_initially(X) iff [
  [X=know_address(b)],
  [X=have_connection]].

holds_at(X,T) iff [
  [X=in_touch_with(B), happens(write(B),T1), not(clipped(T1,in_touch_with(B),T)), T1#<T],
  [holds_initially(X), not(clipped(0,X,T))]].

clipped(T1,X,T) iff [
  [happens(E,T2), terminates(E,X,T2), T1#<T2, T2#<T]].

[happens(write(B),T)] implies [holds_at(have_connection,T)].

[happens(write(B),T)] implies [holds_at(know_address(B),T)].

% Try these queries:
% ?- ciff( 'intouch.alp', [holds_at(in_touch_with(b),3)], A).
% ?- ciff( 'intouch.alp', [holds_at(in_touch_with(b),T), T#=<3], A).