A general architecture for fault tolerant control is proposed. The architecture is based on the ( primary) YJBK parameterization of all stabilizing compensators and uses the dual YJBK parameterization to quantify the performance of the fault tolerant system. The approach suggested can be applied for additive faults, parametric faults and for system structural changes. The modelling for each of these fault classes is described. The method allows for design of passive as well as for active fault handling. Also, the related design method can be fitted either to guarantee stability or to achieve graceful degradation in the sense of guaranteed degraded performance. A number of fault diagnosis problems, fault tolerant control problems, and feedback control with fault rejection problems are formulated/considered, mainly from a fault modelling point of view. The method is illustrated on a servo example including an additive fault and a parametric fault.