Information Technology Reference
In-Depth Information
Model-based diagnosis process is the comparison of predicted device behaviour with its
observed behaviour (Fig. 8).
It is supposed, that the model is correct, and all differences between device behaviour and a
device model indicate availability of broken components.
Main advantages of the model-based approach:
diagnosing the multiple faults;
unexpected fault recognition;
a precision of a component model description does not depend on the expert
experience;
a possibility of new device diagnosing;
multiple using the models;
detailed explanations.
The device
The device
model
The structural
discrepancy
The expected behavior
The observed behavior
The behaviour
discrepancy
Fig. 8. Model-based diagnosis process
6. Assumption-based truth maintenance systems
For building a prognosis network, a component behaviour model, finding minimal conflicts
characterizing irrelevance of observations with prognoses and minimal candidates for a
faulty, it is profitable to use possibilities given by Assumption-based Truth Maintenance
Systems (ATMS) [de Kleer, 1986; Vagin et al., 2008].
The Truth Maintenance Systems (TMS) are the systems dealing with the support of a
coherence in databases. They save the assertions transmitted to them by a problem solver
and are responsible for maintaining their consistency. Each assertion has the justification
describing what kind of premises and assumptions this justification was obtained. The
environment is a set of assumptions.
The inference of an inconsistency characterizes assumption incompatibility within the
presuppositions of which this conclusion was made. Also there is introduced the
environment set which contains some inconsistency [de Kleer, 1986]. The sets of
inconsistency environments E 1 ,E 2 ,...,E m are Nogood = {E 1 ,E 2 ,…,E m }. A consistent ATMS
environment is not Nogood.
There are the following correspondences between ATMS and the model-based diagnosis
approach:
Search WWH ::




Custom Search