When the model-based diagnostic object is deployed, it operates as a highly agile reasoning system, providing dynamic fault isolation without complex diagnostic logic paths. The diagnostic logic is not "fixed" to a pre-determined, static diagnostic tree, but rather performs its reasoning dynamically. The Diagnostician dynamically interprets test results that can come from any source, in any order, and with as many or as few test results at a time as the test source can provide.  Static test trees, on the other hand, are based upon one test result at a time, in a pre-determined sequence, and from a fixed test source. 

Using the Diagnostician, the fundamental nature of diagnostics is uncoupled from test. Test routines make measurements and collect data. The interpretation of the implication of the test/measurement passing or failing is done by the Diagnostician, which dynamically, on-the-fly, interprets test information based upon all information it receives in any order.

The Diagnostician uses both pass and fail results to interpret the "cones of evidence" across the system to efficiently determine the cause of faults. It’s reasoning techniques provide for fast, accurate, flexible diagnostics, and can also isolate the occurrence of multiple fault situations, including multiple independent and multiple dependent (common mode) faults. Static test trees, on the other hand are limited to a single fault assumption and in multiple fault situations, often do not work.