Relational Database to RDF Mapping Patterns.

In order to integrate relational databases into Semantic Web applications, relational databases need to be mapped to RDF. The W3C RDB2RDF Working Group is in the process of ratifying two standards to map relational databases to RDF: Direct Mapping and R2RML mapping language. Through our experience as implementors of two RDB2RDF systems: Ultrawrap and Morph, and as authors of R2RML mappings, we have observed mappings that are reusable in order to solve a commonly occurring problem. In this paper, we have compiled these mappings and present a non-exhaustive list of RDB2RDF Mapping Patterns. We aspire that the mapping patterns in this paper are considered as a starting point for new mapping patterns.