  In recent years, Semantic Web technologies have been increasingly adopted by
researchers, industry and public institutions to describe and link data on the
Web, create web annotations and consume large knowledge graphs like Wikidata
and DBPedia. However, there is still a knowledge gap between ontology
engineers, who design, populate and create knowledge graphs; and web
developers, who need to understand, access and query these knowledge graphs but
are not familiar with ontologies, RDF or SPARQL. In this paper we describe the
Ontology-Based APIs framework (OBA), our approach to automatically create REST
APIs from ontologies while following RESTful API best practices. Given an
ontology (or ontology network) OBA uses standard technologies familiar to web
developers (OpenAPI Specification, JSON) and combines them with W3C standards
(OWL, JSON-LD frames and SPARQL) to create maintainable APIs with
documentation, units tests, automated validation of resources and clients (in
Python, Javascript, etc.) for non Semantic Web experts to access the contents
of a target knowledge graph. We showcase OBA with three examples that
illustrate the capabilities of the framework for different ontologies.
