The fourth lessons starts with an explanation of the principles of **Linked Open Data** (URI, RDF, ontologies, etc.), taken from the "[Introduction to the Principles of Linked Open Data][1]" course by Jonathan Blaney (CC BY) on Programming Historian. In the second part of this lesson, the students learn about **SPARQL**, a query language for LOD. They practise this language by creating queries to search **Wikidata**.
[1]: https://doi.org/10.46430/phen0068