Sparqling: Painlessly drawing SPARQL queries over Graphol ontologies

There is a reason why the proverb says “A picture is worth a thousand words”: diagrams or sketches of concepts and of the relationships that exist between them help understand their meaning. In the Semantic Web, the concepts and relationships of the world are modeled through ontologies, but current standards for ontology languages such as OWL 2 don’t buy into this idea, recurring to formula-based representations, that work well with machines and not so well with humans. Similarly, the languages used to query ontologies, in particular SPARQL, are not immediately intuitive for people who lack specific training or background, so providing graphical support for query formulation can make the life of the end user easier. In this work we present the SPARQLING system for SPARQL query building based on the GRAPHOL visual language for ontologies. The characterizing feature of SPARQLING is the idea to preserve and take advantage of the native diagrammatic representation of GRAPHOL ontologies, allowing the user to navigate it, and to construct a graph-based representation of the query over it through a simple point-and-click mechanism. The system then automatically transforms the graphical query into the SPARQL syntax.