This book describes a set of methods, architectures, and tools to extend the data pipeline at the disposal of developers when they need to publish and consume data from Knowledge Graphs (graph-structured knowledge bases that describe the entities and relations within a domain in a semantically meaningful way) using SPARQL, Web APIs, and JSON. To do so, it focuses on the paradigmatic cases of two middleware software packages, grlc and SPARQL Transformer, which automatically build and run SPARQL-based REST APIs and allow the specification of JSON schema results, respectively. The authors highlight the underlying principles behind these technologies--query management, declarative languages, new levels of indirection, abstraction layers, and separation of concerns--, explain their practical usage, and describe their penetration in research projects and industry. The book, therefore, serves a double purpose: to provide a sound and technical description of tools and methods at the disposal ofpublishers and developers to quickly deploy and consume Web Data APIs on top of Knowledge Graphs; and to propose an extensible and heterogeneous Knowledge Graph access infrastructure that accommodates a growing ecosystem of querying paradigms.
Albert Meroño-Peñuela is a Lecturer (Assistant Professor) in Computer Science and Knowledge Engineering in the Department of Informatics of King's College London (United Kingdom). He obtained his Ph.D. at the Vrije Universiteit Amsterdam in 2016, under the supervision of Frank van Harmelen, Stefan Schlobach, and Andrea Scharnhorst. His research focuses on Knowledge Graphs, Web Querying, and Cultural AI. Albert has participated in large Knowledge Graph infrastructure projects in Europe, such as CLARIAH, DARIAH, and Polifonia H2020, and has published research in ISWC, ESWC, the Semantic Web Journal, and the Journal of Web Semantics. He is, together with Rinke Hoekstra, the original author of grlc, and together with Carlos Martínez-Ortiz, its main current maintainer.Pasquale Lisena is a researcher in the Data Science department at EURECOM, Sophia Antipolis (France). He obtained his Ph.D. in Computer Science from Sorbonne University of Paris in 2019, with a thesis on music representation and recommendation, under the supervision of Raphaël Troncy. His research focuses on Semantic Web, Knowledge Graphs, and Information Extraction, with particular application to the domain of Digital Humanities, contributing on AI projects such as DOREMUS, SILKNOW, and Odeuropa. Pasquale's work has been published in leading conferences in the field, such as ISWC, EKAW, and ISMIR. Given his past background as a web developer, his interest also involves data usability in web applications and human-computer interaction. He is the main author of SPARQL Transformer.Carlos Martínez-Ortiz is a community manager at the Netherlands eScience Center. He obtained his Ph.D. in Computer Science at the University of Exeter (United Kingdom). Afterward, he worked on various research projects at the University of Exeter, Plymouth University, and the eScience Center. These projects were in collaboration with industrial and academic partners in diverse fields such as veterinary science, digital humanities, and life sciences. He has been involved in large projects such as CLARIAH and ODISSEI and works in close collaboration with partners such as SURF, DANS, and The Software Sustainability Institute. His current research interests include linked open data, natural language processing, and software sustainability.
