After the introduction section of Chapter 7, section 7.2 first presents a brief overview of the approaches proposed by the FDI and DX model- based diagnosis communities. Although quite commonplace, this overview is neces- sary because it provides the basic concepts and principles that form the foundations of our comparative analysis. It is followed by the comparison of the mathematical objects used as input of the diagnosis procedures. Section 7.3 then establishes the correspondances of concepts on both sides and compares the techniques used by the two communities. Interestingly, the results obtained by the two approaches are shown to be the same under some assumptions that are exhibited. Finally, Section 7.4 illustrates the DX-FDI MBD bridge with the classical example of the polybox.