Reference data observations for a given system are used to develop a referenceset (102) of such observations. Subsequent observations (comprising, in oneembodiment, current observations) (107) are then used to facilitate selectionof portions of this reference set to yield a resultant set of observations(118) that serves as a model. This model can then be used in comparison toactual system performance to detect, for example, a trend towards a faultycondition. Pursuant to a preferred approach, the model is recomputed from timeto time and, pursuant to a particular embodiment, is recomputed with each newset of current observations.
