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increased intelligence in the system, which AI algorithms have proven useful for demonstrational interfaces, and how we cope with such well-known intelligent-interface-usability issues as knowing what the system can do and what it is doing at any given moment. Demonstrational interfaces allow the user to perform actions on concrete example objects (often using direct manipulation), though the examples represent a more general class of objects. These actions allow the user to create “parameterized” procedures and objects without being required to learn a programming language. We use the term “demonstrational,” because the user demonstrates the desired result through example values. Demonstrational systems vary greatly along many dimensions; some of these systems use inferencing, whereby the system employs heuristics to guess the generalization from the examples; others do not try to infer the generalizations and instead require the user to describe explicitly which of the examples’ properties should be generalized. One way to determine whether a system uses inferencing is that it can perform an incorrect action, even when the user makes no mistakes. A system that doesn’t employ inferencing always performs the correct action if the user is