Data formats
Three data concepts are important: RDF (format), DCAT (vocabulary) and SPARQL (query language).
Data access is described at page data.
RDF (Resource Description Framework)
We focus on graphs consisting of RDF data. The main concepts are described at RDF 1.1 Primer. There are some openHPI online lectures about the Semantic Web; find them by searching for Harald Sack.
DCAT (Data Catalog Vocabulary)
DCAT is an RDF vocabulary which enables to describe datasets and related concepts. The classes of interest are dcat:Dataset and dcat:Distribution (a specific representation of a dataset). DCAT is described at Data Catalog Vocabulary (DCAT) - Version 2.
SPARQL (SPARQL Protocol and RDF Query Language)
Like SQL for relational databases, SPARQL can be used to query RDF databases (triplestores). The specification can be found at SPARQL 1.1 Query Language. Use SELECT to get lists and CONSTRUCT to get graphs. SPARQL examples are available at data.