QueryVOWL: A visual query notation for linked data

Abstract

In order to enable users without any knowledge of RDF and SPARQL to query Linked Data, visual approaches can be helpful by providing graphical support for query building. We present QueryVOWL, a visual query language that is based upon the ontology visualization VOWL and defines mappings to SPARQL. We aim for a language that is intuitive and easy to use, while remaining flexible and preserving most of the expressiveness of SPARQL. In contrast to related work, the queries can be created entirely with visual elements, taking into account RDFS and OWL concepts often used to structure Linked Data. This paper is a revised version of a workshop paper where we first introduced QueryVOWL. We present the query notation, some example queries, and two prototypical implementations of QueryVOWL. Also, we report on a qualitative user study that indicates lay users are able to construct and interpret QueryVOWL graphs.