PG-Keys: Keys for Property Graphs

George Fletcher (TU/e)

I report on a community effort between industry and academia to shape the future of property graph constraints. The standardization for a property graph query language is currently underway through the ISO Graph Query Language (GQL) project. Our position is that this project should pay close attention to schemas and constraints, and should focus next on key constraints. The main purposes of keys are enforcing data integrity and allowing the referencing and identifying of objects. Motivated by use cases from our industry partners, we argue that key constraints should be able to have different modes, which are combinations of basic restriction that require the key to be exclusive, mandatory, and singleton. Moreover, keys should be applicable to nodes, edges, and properties since these all can represent valid real-life entities. Our result is PG-Keys (SIGMOD 2021), a flexible and powerful framework for defining key constraints, which fulfills the above goals. PG-Keys is a design by the Linked Data Benchmark Council’s (LDBC) Property Graph Schema Working Group(PGSWG), consisting of members from industry, academia, and ISO GQL standards group, intending to bring the best of all worlds to property graph practitioners. PG-Keys aims to guide the evolution of the standardization efforts towards making systems more useful, powerful, and expressive.

George Fletcher (PhD, Indiana University Bloomington, 2007) is a full professor of computer and data science and chair of the Database Research Group at Eindhoven University of Technology. His research interests span query language design and engineering, foundations of databases, and data integration. His current primary focus is on management of complex graphs such as social and biological networks. He is co-author of the book “Querying Graphs” (Morgan and Claypool, 2018) on contemporary graph data management and is scientific member of the LDBC’s PGSWG.