Semantic Link Discovery over Relational Data

To make semantic search a reality, we need to be able to efficiently publish large data sets containing rich semantic structure. We have tools for translating relational and semi-structured data into RDF, but such translation tools do not have the goal of adding or providing the kind of semantics necessary to achieve the goals of the Semantic Web and semantic search over the Web. In this chapter, we present LinQuer, a tool for creating semantic links within a data source and between data sources. We focus on link discovery over structured (relational) data since many Semantic Web sources are the result of publishing relational data as RDF and since relational engines provide the scalability and flexibility we need for large scale link discovery. The LinQuer framework is based on the declarative specification of linkage requirements by a user. We present algorithms for translating these requirements to queries that can run over relational data sources, potentially using semantic information (such as a class hierarchy or a more general ontology) to enhance the recall of the link discovery. We show that this framework is flexible enough to permit linking real data, including dirty data (which is commonly found on the Web) and data with a variety of semantic connections.