A key characteristic of effective problem-solving groups is their:

anticipatory breach of contract

as the name suggests, an anticipatory breach is a breach of contract before the time of performance. so, if a promisor denies to perform his promise and signifies his unwillingness before the time for performance, then it is an anticipatory breach of contract.

and

actual breach of contract

while an anticipatory breach is before the time of performance, an actual breach of contract is on the scheduled time of performance of the contract. an actual breach of contract can be committed either.

hope this . : )