Transforming Property Graphs

TL;DR

This paper introduces a declarative framework for property graph transformations using Graph Pattern Calculus, analyzing its complexity, implementing it in openCypher, and demonstrating its practical advantages over ad-hoc methods.

Contribution

It presents a novel declarative approach for property graph transformations based on GPC, including complexity analysis, implementation in openCypher, and empirical evaluation.

Findings

Checking for conflicting property values is PSpace-complete.

The framework is flexible and usable in data integration tasks.

Experimental results show significant practical benefits over ad-hoc scripts.

Abstract

In this paper, we study a declarative framework for specifying transformations of property graphs. In order to express such transformations, we leverage queries formulated in the Graph Pattern Calculus (GPC), which is an abstraction of the common core of recent standard graph query languages, GQL and SQL/PGQ. In contrast to previous frameworks targeting graph topology only, we focus on the impact of data values on the transformations--which is crucial in addressing users needs. In particular, we study the complexity of checking if the transformation rules do not specify conflicting values for properties, and we show this is closely related to the satisfiability problem for GPC. We prove that both problems are PSpace-complete. We have implemented our framework in openCypher. We show the flexibility and usability of our framework by leveraging an existing data integration benchmark, adapting it to our needs. We also evaluate the incurred overhead of detecting potential inconsistencies at run-time, and the impact of several optimization tools in a Cypher-based graph database, by providing a comprehensive comparison of different implementation variants. The results of our experimental study show that our framework exhibits large practical benefits for transforming property graphs compared to ad-hoc transformation scripts.