Patent Number: 
Section: claims

1. A local diagnostic subsystem usable to diagnose a component of a physical system, comprising: at least one observation variable, each observation variable storing a physical value received from a sensor monitoring a first component that describes a state of the first component;  at least one assumption variable, each assumption variable storing a value representing an assumption about the state of the first component;  at least one dependent variable, each dependent variable storing a value representing a quantity relating one of the at least one observation variable to one of the at least one assumption variable;  a plurality of constraints, each constraint relating two of the at least one observation variable, the at least one assumption variable and the at least one dependent variable to describe a behavior of the component; and  at least one diagnosis variable relating a local diagnosis of the local diagnostic subsystem to a second local diagnosis of a second local diagnostic subsystem. 2. The local diagnostic subsystem of  claim 1 , wherein the one or more variables comprise at least one of at least one local pseudo-assumption variable that corresponds to a pseudo-assumption variable of the second local diagnostic subsystem, and at least one local pseudo-observation variable that corresponds to a pseudo-assumption variable of the second local diagnostic subsystem. claim 1 3. A diagnostic system usable to diagnose a component of a physical system, comprising: an initialization circuit, routine or application that initializes the diagnosis system to an initial diagnosis;  a local diagnosis circuit, routine or application that generates one or more candidate local diagnoses based on a physical value received from a sensor monitoring the component, the physical value describing a state of the component;  a diagnosis management circuit, routine or application that selects a local diagnosis from among the one or more candidate local diagnoses; and  a remote diagnosis management circuit, routine or application that communicates with a second diagnostic system, wherein zero, one or more of the candidate local diagnoses are based in part on a second local diagnosis generated by the second diagnostic system. 4. A method for diagnosing a physical system, the system comprising a plurality of physical components being diagnosed by a plurality of local diagnostic subsystems, the method comprising: initializing a first local diagnostic subsystem to an initial diagnosis;  assigning an observation value to an observation variable of the first local diagnostic subsystem, wherein the observation value corresponds to a physical value received from a sensor monitoring a first component and describing a state of the first component;  performing a first local diagnosis in the first local diagnostic subsystem to determine a minimal cost diagnosis explaining the observation value;  determining whether the lowest cost diagnosis requires a change in the value of a pseudo-assumption variable of the first local diagnostic subsystem to a desired value;  performing a second local diagnosis in the first local diagnostic subsystem in which the value of the pseudo-assumption variable is held constant to determine a maximum cost;  supplying a desired value and the determined maximum cost to a second local diagnostic subsystem where the second local diagnostic subsystem contains a pseudo-observation variable corresponding to the pseudo-assumption variable of the first local diagnostic subsystem;  performing a third local diagnosis in the second local diagnostic subsystem to determine whether a diagnosis in which the pseudo-observation variable is set to the desired value can be performed for a cost less than the maximum cost;  adopting the first local diagnosis in the first local diagnostic subsystem when the third local diagnosis can not be performed for a cost less than the maximum cost; and  adopting the second local diagnosis in the first local diagnostic subsystem when the third local diagnosis can be performed for a cost less than the maximum cost.