An Environment for Acquiring Semantic Information

AN ENVIRONMENT FOR ACQUIRING SEMANTIC INFORMATION Damaris M. Ayuso, Varda Shaked, and Ralph M. Weischedel BBN Laboratories Inc. 10 Moulton St. Cambridge, MA 02238 Abstract An improved version of IRACQ (for Interpretation Rule ACQuisition) is presented. I Our approach to semantic knowledge acquisition: 1 ) is in the context of a general purpose NL interface rather than one that accesses only databases, 2) employs a knowledge representation formalism with limited inferencing capabilities, 3) assumes a trained person but not an AI expert, and 4) provides a complete environment for not only acquiring semantic knowledge, but also main- taining and editing it in a consistent knowledge base. IRACQ is currently in use at the Naval Ocean Sys- tems Center. 1 Introduction The existence of commercial natural language in- terfaces (NLI's), such as INTELLECT from Artificial Intelligence Corporation and Q&A from Symantec, shows that NLI technology provides utility as an inter- face to computer systems. The success of all NLI technology is predicated upon the availability of sub- stantial knowledge bases containing information about the syntax and semantics of words, phrases, and idioms, as well as knowledge of the domain and of discourse context. A number of systems demonstrate a high degree of transportability, in the sense that software modules do not have to be changed when moving the technology to a new domain area; only the declarative, domain specific knowledge need be changed. However, creating the knowledge bases requires substantial effort, and therefore substantial cost. It is this assessment of the state of the art that causes us to conclude that know~edge acquisition is one of the most fundamenta/ prob/ems to widespread applicability of NLI techno/ogy. This paper describes our contribution to the ac- quisition of semantic knowledge as evidenced in IRACQ (for Interpretation Rule ACQuisition), within the context of our overall approach to representation of domain knowledge and its use in the IRUS natural language system [5, 6,271. An initial version of IRACQ was reported in [19]. Using IRACQ, mappings 1The work presented here was supported under DARPA contract #N00014-85-C-0016. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessenly representing the officual policies, either expressed or implied, of the Defense Advanced Research Projects Agency or of the United States Government. between valid English constructs and predicates of the domain may be defined by entering sample phrases. The mappings, or interpretation rules (IRules), may be defined for nouns, verbs, adjectives, and prepositions. IRules are used by the semantic interpreter in enforcing selectional restrictions and producing a logical form as the meaning represen- tation of the input sentence. IRACQ makes extensive use of information present in a model of the domain, which is represented using NIKL [18, 21], the terminological reasoning component of KL-TWO [26]. Information from the domain model is used in guiding the IRACQ/user interaction, assuring that acquisition and editing yield IRules consistent with the model. Further support exists for the IRule developer through a flexible editing and debugging …

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