/* GENKN : Bits of general knowledge about certain objects

						Updated: 5 February 81
*/


isa(period,always).
isa(point,origin).
isa(line,axis(x)).
isa(line,axis(y)).
isa(line,axis(z)).

:- dbentry( tangent(axis(x),[0,0]) ).
:- dbentry( tangent(axis(y),[90,0]) ).
:- dbentry( tangent(axis(z),[0,90]) ).

:- dbentry( on(origin,axis(x)) ).
:- dbentry( on(origin,axis(y)) ).
:- dbentry( on(origin,axis(z)) ).




