V1: A Visual Query Language for Property Graphs

The property graph is an increasingly popular data model. Pattern construction and pattern matching are important tasks when dealing with property graphs. Given a property graph schema S, a property graph G, and a query pattern P, all expressed in language L, pattern matching is the process of finding, merging, and annotating subgraphs of G that match P. Expressive pattern languages support topological constraints, property values constraints, negations, quantifications, aggregations, and path semantics. Calculated properties may be defined for vertices, edges, and subgraphs, and constraints may be imposed on their evaluation result. Query posers would like to construct patterns with minimal effort, minimal trial and error, and in a manner that is coherent with the way they think. The ability to express patterns in a way that is aligned with their mental processes is crucial to the flow of their work and to the quality of the insights they can draw. Since the capabilities of the human visual system with respect to pattern perception are remarkable, it is a matter of course that query patterns were to be expressed visually. Visual query languages have the potential to be much more 'user-friendly' than their textual counterparts in the sense that patterns may be constructed and understood much more quickly and with much less mental effort. A long-standing challenge is to design a visual query language that is generic, has rich expressive power, and is highly receptive and productive. V1 attempts to answer this challenge. V1 is a declarative visual pattern query language for schema-based property graphs. V1 supports property graphs with mixed (both directed and undirected) edges and unary edges, with multivalued and composite properties, and with null property values. V1 is generic, concise, has rich expressive power, and is highly receptive and productive.