A retrieval model based on an extended modal logic and its application to the RIME experimental approach

This paper focuses on the query processing module of RIME, an experimental prototype of an intelligent information retrieval system designed to manage high-precision queries on a corpus of medical reports. Though highly specific this particular corpus is representative of an important class of applications: information retrieval among full-text specialized documents which constitute critical sources of information in several organizations (medicine, law, space industry…). This experience allowed us to design and implement an elaborate model for the semantic content of the documents which is an extension of the Conceptual Dependency approach. The underlying retrieval model is inspired from the Logic model proposed by C.J. Van Rijsbergen, which has been considerably refined using an Extended Modal Logic. After presenting the context of the RIME project, we briefly describe the models designed for the internal representation of medical reports and queries. The main part of the paper is then devoted to the retrieval model and its application to the query processing module of RIME which has a natural language interface. Processing a query involves two main phases: the interpretation which transforms the natural language query into a search expression, and the evaluation phases which retrieves the corresponding medical reports. We focus here on the evaluation phases and show its relationship with the underlying retrieval model. Evaluations from practical experiments are also given, along with indications about current developments of the project.