A classification of real-time where infrequent deadline misses are tolerable, but may degrade system quality, and a result received after its deadline is considered not useful.
From the real-time computing wikipedia page:
Firm: Infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
An example might be a system that serves glasses of milk. If the system serves milk after its expiration date, the serving is useless. However, eating cereal without milk is tolerable, but not desirable.
