A Visual Language for Querying and Updating Graphs

QGRAPH is a new visual language for querying and updating graph databases. In QGRAPH the user can draw a query consisting of some vertices and edges with specified relations between their attributes. The response will be the collection of all subgraphs of the database that have the desired pattern. QGRAPH is very useful for knowledge discovery. QGRAPH has a powerful and elegant counting feature that enables the user to easily specify how many of certain objects and links should exist in order for a subgraph to match a query. QGRAPH has a clean formal semantics which we describe in detail. We show that QGRAPH has expressive power corresponding to a well-defined subset of FO(COUNT), i.e., first-order logic with counting quantifiers.