(a) Hidden understandings are unfair and illegal.
(b) The obligation is always on the user of a system or
convention to show that he has made a sufficiently clear
statement of his method. The benefit of any doubt is given
against the player who bears the onus to disclose his methods.
(c) Opponents are entitled to know of any conditions
attaching to the meaning of a call.If possible holdings are
excluded by the existence of an alternative call to cover
them, then this must be disclosed.
(d) A bid may be forcing by partnership agreement, but it is
not improper for a player to break that agreement and pass in
a forcing situation provided that there is no understanding in
the partnership that it will happen.
A partnership agreement is an arrangement between partners of which opponents are entitled to be informed, but it does not constitute an undertaking to opponents.