An expert system shell is software to both create and execute an expert system. This will normally include components to store a knowledge base of facts and rules, a reasoning system, an explanation component and a user interface. Using a shell is typically faster and easier than creating a bespoke expert system, but will also have limitations. In particular, the type of reasoning may be fixed by the specific shell, and different shells may be more suitable for different domains.
Used in Chap. 18: pages 299, 311