Defining Schemas for Property Graphs by using the GraphQL Schema Definition Language

GraphQL is a highly popular new approach to build Web APIs. An important component of this approach is the GraphQL schema definition language (SDL). The original purpose of this language is to define a so-called GraphQL schema that specifies the types of objects that can be queried when accessing a specific GraphQL Web API. This paper focuses on the question: Can we repurpose this language to define schemas for graph databases that are based on the Property Graph model? This question is relevant because there does not exist a commonly adopted approach to define schemas for Property Graphs, and because the form in which GraphQL APIs represent their underlying data sources is very similar to the Property Graph model. To answer the question we propose an approach to adopt the GraphQL SDL for Property Graph schemas. We define this approach formally and show its fundamental properties.