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I’ve been working on understanding thoroughly how RDF datasets used in SPARQL 1.1 are defined and how named graphs and GRAPH graph patterns are evaluated. I have based this write-up solely on the SPARQL 1.1 specification (mostly section 13) and intentionally not on how existing SPARQL engines or stores actually work.

When evaluating a SPARQL query, the query is answered in the context of an RDF dataset. An RDF dataset is comprised of 1 default graph and 0 or more named graphs. Each named graph holds RDF triples. Triples may be included in one or more of the default graph or named graphs but are considered independently when coming from each graph (for example, blank nodes are not comparable).

There are three places a dataset can be defined:

1. Query processor – by default, the query processor will interpret