Abstract: To effectively manage operations and maintenance of engineered systems, the key performance indicators of the systems should be quantitatively evaluated and monitored. The systems' performances are usually described by a multi-level indicator framework. A set of directly measureable parameters or variables are located at its bottom, the aggregated indicators are in the middle-levels and the overall in-service quality indices or the like (e.g., health index) are at the top. To clarify the meaning and uses of quality indices and indicator framework, a literature review on them is carried out and relevant issues are discussed. It is found that the overall and comprehensive performance of a system is described by one or more quality indices, and the method to derive the quality indices is multi-criteria analysis. The main applications of the performance evaluation framework and quality indices include health evaluation, monitoring or regulation, issue tracking as well as operation and maintenance decisions. Different from condition monitoring and fault diagnosis, the quality-indices-based performance monitoring and tracking is usually conducted periodically and applicable for monitoring and controlling of overall performances of complex engineered systems as well as mid-long term management of the systems. The reviewed methods and typical case studies have reference meaning to the supervising, operation and maintenance management of complex engineered systems.

Key words: engineered systems, performance evaluation, in-service quality indices, indicator system, literature review