CoXML: Cooperative XML Query Answering?

Abstract

AbstractThe heterogeneity nature of XML data creates the need for approximate query answering. Approximate answers may be derived by relaxing query conditions to less restricted forms, i.e.,query relaxation. In this article, we first present an approach to XML query relaxation based on schema conversion, which leverages on the value relaxation techniques in the relational model. This approach, however, does not support structure relaxation. Also, information may be lost during schema conversion. To remedy these shortcomings, we then present a cooperative XML (CoXML) system provides user‐specific approximate query answers directly in the XML model. The key features of the system include:a query language that allows users to specify approximate query conditions and relaxation control requirements;a relaxation index structure, XTAH, that enables the system to provide user‐desired relaxations as specified in the queries; anda ranking model that incorporates both content and structure similarities in evaluating the relevancy of approximate answers.We also present a scalable and extensible architecture for the CoXML system based on mediators. Finally, we evaluate the system using the INEX test collections. The evaluation results demonstrate the effectiveness of the system in providing user‐specific relaxation.