With the growing use of complex systems, there has been considerable interest in the development of techniques to detect and isolate faults. An undetected fault in a system can have catastrophic effects such as loss of human life, environmental pollution and financial losses. Examples of places where FDI schemes can be useful are hospitals and manufacturing companies. In hospitals, staff would need to be aware of faults in health monitoring equipment (e.g. electrocardiographs) to avoid incorrect patient health diagnosis. On the other hand an undetected fault in a production line can eventually require overall plant shutdown, which can be costly. The literature and effort gone into the field of FDI is overwhelming. It still remains one of the most active areas of research today. Owing to this, one can expect the terminology to be quite misleading as different authors assign different terms to describe similar concepts.