0. How does the distribution of RDF data in SANSA work?

SANSA uses the RDF data model for representing graphs consisting of triples with subject, predicate and object. RDF datasets may contains multiple RDF graphs and record information about each graph, allowing any of the upper layers of sansa (Querying and ML) to make queries that involve information from more than one graph. Instead of directly dealing with RDF datasets, the target RDF datasets need to be converted into an RDD of triples. We name such an RDD a main dataset. The main dataset is based on an RDD data structure, which is a basic building block of the Spark framework. RDDs are in-memory collections of records that can be operated on in parallel on large clusters.