(12th-August-2020)
• Making assumptions about what is working normally, and deriving what components could be abnormal, is the basis of consistency-based diagnosis. Suppose a fault is something that is wrong with a system. The aim of consistency-based diagnosis is to determine the possible faults based on a model of the system and observations of the system. By making the absence of faults assumable, conflicts can be used to prove what is wrong with the system.
• For example, the house wiring example depicted in Figure 5.2 and represented in Example 5.5. A background knowledge base suitable for consistency-based diagnosis is given in Figure 5.8. Normality assumptions are added to the clauses to make explicit the assumption that the components work. We have added conditions that switches, circuit breakers, and lights must be okay to work as expected. There are no clauses for the ok atoms, but they are made assumable.
• The user is able to observe the switch positions and whether a light is lit or dark.
• A light cannot be both lit and dark. This knowledge is stated in the following integrity constraints:
• false ←dark_l1 ∧lit_l1.
• false ←dark_l2 ∧lit_l2.
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