QUOGGLES: Query On Graphs - A Graphical Largely Extensible System

We describe the query and data processing language QUOGGLES which is particularly designed for the application on graphs. It uses a pipeline-like technique known from command line processing, and composes its queries as directed acyclic graphs. The main focus is on the extensibility and the ease of use. The language permits queries that select a distinguished subgraph, e.g., the set of all green nodes with degree at least d or the set of edges whose endnodes have a neighbor which has exactly one neighbor. It is SQL complete, however, it cannot describe paths of arbitrary length; otherwise NP-hard problems like Hamilton path could directly be expressed. QUOGGLES also enables the user to concatenate queries with algorithms, e.g. with graph drawing algorithms, which are then applied to the selected subgraph.