A diagnostic system for identifying a component that has failed, the diagnostic system comprising: an interface for receiving input relating to observed symptoms indicative of a failed component; a processing element for correlating the input relating to the observed symptoms with one or more suspect components that are each capable of causing the observed symptoms upon failure, said processing element capable of prioritizing the plurality of suspect components based upon a relative likelihood that the respective suspect components caused the observed symptoms, said processing element also capable of identifying at least one test to be performed in order to refine the prioritization of the plurality of suspect components; and a display for presenting a prioritized listing of the plurality of suspect components and an indication of the at least one test to be performed in order to refine the prioritization of the plurality of suspect components, wherein said processing element correlates the input relating to the observed symptoms with the at least one suspect component in accordance with a diagnostic model constructed based upon systemic information relating to the components and input-output relationships of the components, experiential information relating to direct relationships between component failures and the observed symptoms, and factual information relating to component reliability, and wherein said processing element correlates the input relating to the observed symptoms with the at least one suspect component in accordance with the diagnostic model comprising a plurality of nodes and a plurality of arcs that interconnect the nodes in a manner defined by the systemic information and the experiential information, wherein the plurality of nodes include nodes representing the components and the observed symptoms, wherein each node has at least two states, and wherein the diagnostic model assigns a probability to each state of a node based upon at least one of the systemic information, the experiential information and the factual information. an interface for receiving input relating to observed symptoms indicative of a failed component; a processing element for correlating the input relating to the observed symptoms with one or more suspect components that are each capable of causing the observed symptoms upon failure, said processing element capable of prioritizing the plurality of suspect components based upon a relative likelihood that the respective suspect components caused the observed symptoms, said processing element also capable of identifying at least one test to be performed in order to refine the prioritization of the plurality of suspect components; and a display for presenting a prioritized listing of the plurality of suspect components and an indication of the at least one test to be performed in order to refine the prioritization of the plurality of suspect components, wherein said processing element correlates the input relating to the observed symptoms with the at least one suspect component in accordance with a diagnostic model constructed based upon systemic information relating to the components and input-output relationships of the components, experiential information relating to direct relationships between component failures and the observed symptoms, and factual information relating to component reliability, and wherein said processing element correlates the input relating to the observed symptoms with the at least one suspect component in accordance with the diagnostic model comprising a plurality of nodes and a plurality of arcs that interconnect the nodes in a manner defined by the systemic information and the experiential information, wherein the plurality of nodes include nodes representing the components and the observed symptoms, wherein each node has at least two states, and wherein the diagnostic model assigns a probability to each state of a node based upon at least one of the systemic information, the experiential information and the factual information.