Abstract: An n-tuple defines an envelope of a variable over a time interval. An input memory receives blocks of measurements made at known points of the network and converts them into initial n-tuples. In a base memory, a functional model comprises a list of components, (Lv), and the designation (Df, Dg) of at least one particular function of the measurements (Lp). Management will, repetitively, (a) match together available initial n-tuples, and at least one model applicable to them, (b) through computations on n-tuples, with the function designation (Df, Dg) of the model, and these n-tuples, obtain at least one result n-tuple (Nf, Ng), (c) apply the result n-tuple (Nf, Ng) to test for a standard expression, and (d) associate the output from the test with the list of components (Lv) of the model. Decision logic analyzes various outputs from the test, with a view to determining one or more defective components.