We propose to demonstrate an interactive system called SPARQLIt, assisting users in the formulation of SPARQL queries. In SPARQLIt, users start by specifying a well-structured SPARQL query; the challenge is that the query may not be grounded to a specific ontology schema or content. The space of possible grounded queries to which the user query may be mapped is then well-defined, and SPARQLIt allows the user to interactively explore this space in a systematic way. A key component of this exploration is a pruning mechanism that is based on identifying query parts that are correct/incorrect, and using them to efficiently filter candidate queries of a certain form. Our demonstration will use the Yago Ontology to exemplify the ease of constructing queries with SPARQLIt without prior knowledge of its contents. We will allow participants to specify queries of their choice and will walk them through the interactive process of query refinement.