The first installment in a two part series of articles that reports on the development of an expert system for assisting in the engineering of worsted fabrics addresses the process of fabric engineering and the structure, components, and functional features of the recently developed worsted fabric expert system (WOFAX), including software development tools, user interface, inference engine, and knowledge base. The knowledge and models in WOFAX include composition, weave, set and yarn count, yarn type, twist, fiber, and finishing advisor; neural network models for predicting fabric properties; database; and fabric performance and FAST interpreters. WOFAX issues a summary report that is displayed on screen, exported to a text file, or printed as hard copy. Typical reports specify fabric composition and construction, yarn type and yarn twist, fiber fineness, weaving recommendations, finishing sequences, and predicted performance. 16 refs.