This is the last in my series on commitments, where we look at what happens when debtors don’t satisfy their commitments.

A debtor agent makes a commitment before satisfying the commitment.  In fact, that’s the whole point of using commitments.  It is a way for a debtor to tell others what it will do in the future.  Since debtors are assessed penalties when they fail to satisfy a commitment, they are certainly encouraged to do satisfy. However, bad things can happen between making and satisfying a commitment.

To paraphrase Spock in The Wrath of Khan, “There are two possibilities. They are unable to respond. They are unwilling to respond”.  First, a debtor may be unable to satisfy all of its commitments.  Toyota had a lot of commitments to deliver automobiles, but when the tsunami hit it, Toyota was no longer able to keep all of those commitments.

Second, event considering the cost of penalties, a debtor may be unwilling to satisfy all of its commitments.  Airlines knowingly overbook flights, creating more commitments than they can possibly keep.  They willing pay the penalties for their broken commitments.  This covers the case where debtors originally intended in good faith to satisfy their commitments but it is no longer profitable to do so, and where debtors made a commitment never intending to satisfy them.  We don’t distinguish between good and bad intentions in our commitment formalism, because it makes little difference and it is often impossible to distinguish anyway.

To model real world situations, we have to allow these messy cases.  We can not require debtors to always satisfy their commitments. The only thing we do require is that debtors must not leave their commitments hanging forever.  If they can’t satisfy a commitment, then then must eventually cancel it.   Commitment cancellation could be triggered by a timeout mechanism.