isa(X,Y) :-
	is_a(X,Y).

isa(X,Y) :-
	is_a(X,Z),
	isa(Z,Y).
is_a(board,device).
is_a(motherboard,device).
is_a(agent,object).
is_a(device,object).
is_a(object,inca_node).
is_a(constraint,inca_constraint).
is_a(dynamic_constraint,constraint).
is_a(static_constraint,constraint).
