SparqlFilterFlow provides a visual interface for the composition of SPARQL queries. It is based on the intuitive and empirically well-founded filter/flow model that has been extended to address the unique specifics of SPARQL and RDF. In contrast to related work, no structured text input is required but the queries can be created entirely with graphical elements.
A related project based on the VOWL notation is QueryVOWL.
The web demo is a lightweight version of SparqlFilterFlow that gives an idea of the approach. It provides limited functionality and lacks many of the key features, such as chaining different filter nodes in an arbitrary order, or splitting up a flow into several result sets.
Haag, F.; Lohmann, S.; Bold, S.; Ertl, T. (2014): Visual SPARQL Querying based on Extended Filter/Flow Graphs. Proceedings of the 12th International Working Conference on Advanced Visual Interfaces (AVI '14), pp. 305-312. New York, NY, USA: ACM, 2014.
Haag, F.; Lohmann, S.; Ertl, T. (2014): SparqlFilterFlow: SPARQL Query Composition for Everyone. Proceedings of ESWC 2014 Satellite Events, pp. 362-367. Heidelberg: Springer, LNCS 8798, 2014.