TY - JOUR AU - Myłka, Antoni AU - Myłka, Alina AU - Kryza, Bartosz AU - Kitowski, Jacek PY - 2012/06/20 Y2 - 2024/03/29 TI - Integration of Heterogeneous Data Sources in an Ontological Knowledge Base JF - COMPUTING AND INFORMATICS JA - Comput. Inform. VL - 31 IS - 1 SE - Articles DO - UR - https://www.cai.sk/ojs/index.php/cai/article/view/2089 SP - 189-223 AB - In this paper we present X2R, a system for integrating heterogeneous data sources in an ontological knowledge base. The main goal of the system is to create a unified view of information stored in relational, XML and LDAP data sources within an organization, expressed in RDF using a common ontology and valid according to a prescribed set of integrity constraints. X2R supports a wide range of source schemas and target ontologies by allowing the user to define potentially complex transformations of data between the original data source and the unified knowledge base. A rich set of integrity constraint primitives has been provided to ensure the quality of the unified data set. They are also leveraged in a novel approach towards semantic optimization of SPARQL queries. ER -