Querying heterogeneous linked building data with context-expanded GraphQL queries

Linked Data in the construction industry is a topic gaining serious interest over the last years. However, this interest remains largely academic and has not sparked much adoption of web technologies in the field. To nourish adoption of Linked Data in practice, access to the data has to be made more easy. SPARQL, the recommended RDF query language, has proven very powerful for retrieving and updating RDF datasets. However, due to its verbosity and complexity, it is often considered a threshold for developers to implement in their tools. In this paper, we compare SPARQL with Linked Data querying languages that extend the GraphQL syntax, in context of querying building datasets: HyperGraphQL and GraphQL-LD. Since it went open source in 2015, GraphQL has been adopted by a large community of developers, partly due to its elegance and conciseness. As a use case, the queries are performed on an RDF-based multi-model that relies on the recent ISO standard ICDD (ISO 21597). ICDD interlinks information on a sub-document identifier level, based on OWL. It is aimed at the industry in that it adds a layer of Linked Data to documentation formats that are still widely used in practice: IFC, spreadsheets, imagery etc. Therefore, it is considered a tuned use case for comparing these different RDF query languages.