What do we mean by expert systems

The purpose of this paper is to expose readers to the concept and vocabulary of expert systems, especially in the context of scientific software, and to introduce a number of related topics such as knowledge-based systems. The role of expertise is discussed, as well as the view of an expert system as an expert performance and expert modelling system. Some views and experience of statisticians (in the field of expert systems) are noted, and in particular their ideas about the existence or non-existence of (genuine) expert systems are discussed.