STTL - A SPARQL-based Transformation Language for RDF

The general research question addressed in this paper is: "How to transform RDF into other languages". This is of prime interest to present data selected and extracted from the Web of data in a format suitable for the user (e.g., HTML or CSV). Moreover, RDF can be viewed as a meta-model to represent on the Web of data other languages and models. The above research question then becomes: "How to generate the concrete syntax of expressions of a given language from their RDF representation". To answer these questions, we present SPARQL Template Transformation Language (STTL), a generic RDF transformation rule language, independent from the output language. We conceived it as a lightweight syntactic extension to SPARQL and we show how to compile it into standard SPARQL. We present a generic transformation rule engine implementing STTL and several RDF transformers we defined for various output languages, showing STTL's expressive power.