SparqlBlocks: Using Blocks to Design Structured Linked Data Queries

While many Linked Data sources are available, the task of building structured queries on them is still a challenging one for users who are not conversant in the specialised query languages required for their effective use. A key hindering factor is the lack of intuitive user interfaces for these languages. The block programming paradigm is becoming popular for the development of visual interfaces that are easy to use and guaranteed to generate syntactically correct programs, promoting a gradual and modular approach to the task of programming. We exploit these features of the block paradigm to develop SparqlBlocks, a visual language and an integrated user interface in which both Linked Data queries and results are represented as blocks, supporting a modular and exploratory approach to query design. By integrating the presentation of queries and results, reuse of results in the refinement of queries is promoted, as well as the exploration of both the data and the structure of Linked Data sources. SparqlBlocks has been evaluated with 11 users literate in computer science but with small to no expertise in querying Linked Data. After a tutorial, all the users were able to build at least a simple query and all but two were able to build nontrivial queries.