How to use expert systems to design front ends for existing software, including such popular programs as Lotus 1-2-3 and dBASE. This unique guide shows you how to construct elegant user interfaces independent of the underlying software, make an intelligent front end that permits creation of data validation routines at the entry point for spreadsheets (which is all but impossible without expert systems technology), and write a natural-language front end that enables the user to interact with a spreadsheet well above the call level. Contains example screens, case studies, and complete rule listings.