It is used in expert systems when logical rules relate the input data and assertions to goals and subgoals but the data is often expressed in terms of likelihood rather than certainty.

• 当逻辑规则把输入数据和判定与目标或子目标联系起来时，它可用于专家系统，但此时数据常常是用似然语言而不是用确定语言表示。