Milord II allows the programmer to give a value to a parameter that controls the minimum truth-value that a premise has to evaluate to in order to fire a rule in that particular module.
This parameter is named the threshold of a module. Its value is a linguistic term and the default value is the second term of the chain of truth-values (see Section 4). MYCIN  had certainty factors lying in the interval [-1,1], and used a similar approach by having a threshold to fire rules of 0.2. An example of threshold declaration is:
Truth Threshold: may_be
As another consequence of the threshold parameter all facts with a lower truth-value less or equal than the threshold become unknown.