Graph databases are becoming pervasive in several application scenarios such as the Semantic Web, social and biological networks, and geographical databases, to name a few. However, specifying a graph query is a cumbersome task for non-expert users because graph databases (i) are usually of large size hence difficult to visualize and (ii) do not carry proper metadata as there is no clear distinction between the instances and the schemas. We present GPS, a system for interactive path query specification on graph databases, which assists the user to specify path queries defined by regular expressions. The user is interactively asked to visualize small fragments of the graph and to label nodes of interest as positive or negative, depending on whether or not she would like the nodes as part of the query result. After each interaction, the system prunes the uninformative nodes i.e., those that do not add any information about the user's goal query. Thus, the system also guides the user to specify her goal query with a minimal number of interactions.