Abstract-Query relaxation refers to the process of reducing the number of constraints on a query if it returns no result when searching a database. This is an important process to enable extraction of an appropriate number of query results because queries that are too strictly constrained may return no result, whereas queries that are too loosely constrained may return too many results. This paper proposes an automated method of correlation-based query relaxation (CBQR) to select an appropriate constraint subset. The example-based dialog modeling framework was used to validate our algorithm. Preliminary results show that the proposed method facilitates the automation of query relaxation. We believe that the CBQR algorithm effectively relaxes constraints on failed queries to return more dialog examples.
I. INTRODUCTIONA query consists of a set of attribute-value pairs in a relational database. These pairs are carefully chosen to include only a specified subset of the database. If constraints on the query are too strict, it may fail to produce an answer. Constraints on queries that fail to produce an answer (failed queries) are relaxed to satisfy more tuples so that queries can return relevant answers [1][2][3][4].We here suggest a simple correlation-based algorithm for relaxing constraints on failed queries for an example-based dialog modeling (EBDM) framework [5]. In the EBDM framework, a query (e.g., a set of semantic and discourse constraints) returns semantically-similar dialog examples to predict the next system action. However, failed queries are inevitable because of the data sparseness problem or because of prior errors by the speech recognition and language understanding modules. To avoid this problem, query constraints are relaxed using heuristic relaxation strategies so that more matches are found. However, these strategies cannot cover all situations perfectly because the strategies are prepared manually by human experts and it is difficult to know which query constraints should be relaxed in a specific situation. Therefore, this paper proposes a correlation-based query relaxation (CBQR) algorithm that uses correlation coefficients between pairs of query constraints to automatically select a constraint subset by removing irrelevant constraints.