Issues in the development of natural language front-ends

This paper will discuss some issues we believe to be important to the design of a natural language front-end. These are divided into three categories: conceptual coverage, linguistic coverage, and implementation issues. The section on conceptual coverage discusses the use of a domain expert, which understands what the user is saying even though the system to which the front-end is interfaced might not be able to properly do what the user wants. The section on linguistic coverage discusses attempts to allow a natural language interface to handle natural, interactive human communication. Two solutions are explored: First, the design of a robust natural-language-understanding system, composed of many experts that know about some aspect of the organization of language, is considered; second, because the design of a robust system is a large task, the intermediate goal of limiting the vocabulary and constructions that can be used while retaining all the user-oriented benefits of natural language is considered. The implementation issues considered are the design of a system in which the grammar and the domain of discourse can be easily extended and which can be used for more than one domain without extensive rewrite.