External authors:

• Domagoj Vrgoc ( Pontificia Universidad Catolica de Chile , Inst Milenio Fundamentosdelos Datos IMFD )
• Carlos Rojas ( Inst Milenio Fundamentosdelos Datos IMFD )
• Renzo Angles ( Universidad de Talca , Inst Milenio Fundamentosdelos Datos IMFD )
• Carlos Buil-Aranda ( Universidad Tecnica Federico Santa Maria , Inst Milenio Fundamentosdelos Datos IMFD )
• Aidan Hogan ( Universidad de Chile , Inst Milenio Fundamentosdelos Datos IMFD )
• Gonzalo Navarro ( Universidad de Chile , Inst Milenio Fundamentosdelos Datos IMFD )
• Juan Romero ( Pontificia Universidad Catolica de Chile , Inst Milenio Fundamentosdelos Datos IMFD )

Abstract:

In this systems paper, we present MillenniumDB: a novel graph database engine that is modular, persistent, and open source. MillenniumDB is based on a graph data model, which we call domain graphs, that provides a simple abstraction upon which a variety of popular graph models can be supported, thus providing a flexible data management engine for diverse types of knowledge graph. The engine itself is founded on a combination of tried and tested techniques from relational data management, state-of-the-art algorithms for worst-case-optimal joins, as well as graph-specific algorithms for evaluating path queries. In this paper, we present the main design principles underlying MillenniumDB, describing the abstract graph model and query semantics supported, the concrete data model and query syntax implemented, as well as the storage, indexing, query planning and query evaluation techniques used. We evaluate MillenniumDB over real-world data and queries from the Wikidata knowledge graph, where we find that it outperforms other popular persistent graph database engines (including both enterprise and open source alternatives) that support similar query features.