Interaction of Knowledge Sources in a Portable Natural Language Interface

Interaction of Knowledge Sources in a Portable Natural Language Interface Carole D. Hafner Computer Science Department General Motors Research Laboratories Warren, MI 48090 Abstract This paper describes a general approach to the design of natural language interfaces that has evolved during the development of DATALOG, an Eng- lish database query system based on Cascaded ATN grammar. By providing separate representation schemes for linguistic knowledge, general world knowledge, and application domain knowledge, DATALOG achieves a high degree of portability and extendability. 1. Introduction An area of continuing interest and challenge in computational linguistics is the development of techniques for building portable natural language (NL) interfaces (See, for example, [9,3,12]). The investigation of this problem has led to several NL systemS, including TEAM [7], IRUS [i], and INTELLECT [10], which separate domain-dependent information from other, more general capabilities, and thus have the ability to be transported from one application to another. However, it is impor- tant to realize that the domain-independent por- tions of such systems constrain both the form and the content of the domain-dependent portions. Thus, in order to understand a system's capabili- ties, one must have a clear picture of the struc- ture of interaction among these modules. This paper describes a general approach to the design of NL interfaces, focusing on the structure of interaction among the components of a portable NL system. The approach has evolved during the development of DATALOG (for "database dialogue") an esperimental system that accepts a wide variety of English queries and commands and retreives the answer from the user's database. If no items sat- isfy the user's request, DATALOG gives an informa- tive response explaining what part of the query could not be satisfied. (Generation of responses in DATALOG is described in another report [6].) Although DATALOG is primarily a testbed for research, it has been applied to several demon- stration databases ~nd one "real" database con- taining descriptions and rental information for more than 500 computer hardware units. The portability of DATALOG is based on the independent specification of three kinds of knowl- edge that such a system must have: a linguistic grammar of English; a general semantic model of database objects and relationships; and a domain model representing the particular concepts of the application domain. After giving a brief overview of the architecture of DATALOG, the remainder of the paper will focus on the interactions among the components of the system, first describing the interaction between syntax and semantics, and then the interaction between general knowledge and domain knowledge. 2. Overview of DATALOG Architecture The architecture of DATALOG is based on Cas- caded ATN grammar, a general approach to the design of language processors which is an exten- sion of Augmented Transition Network grammar [13]. The Cascaded ATN approach to NL processing was first developed in the RUS parser [2] and was for- mally characterized by Woods [14]. Figure 1 shows the architecture of a Cascaded ATN for NL process- ing: the syntactic-and semantic components are implemented as separate processes …

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