Cytosm: Declarative Property Graph Queries Without Data Migration

The property graph model has recently gained significant popularity, combining great expressiveness with powerful declarative graph query languages. However, in order to take advantage of these features, data must be loaded into a specialised graph database. Additionally, property graphs are often schema-free, complicating efficient query execution. In this paper we present Cytosm, a middleware application which enables the execution of property graph queries, on non-graph databases, without data migration. Cytosm relies on gTop, a schema containing an abstract property graph topology, and its mapping to specific database backends. Cytosm uses gTop to efficiently execute OpenCypher queries, exploiting schema information to optimise the query plan, and mapping query concepts to the relational backend. Our experiments show that Cytosm achieves competitive query execution times on relational backends, when compared to leading graph databases.