  Over the past few years, we have seen the emergence of large knowledge graphs
combining information from multiple sources. Sometimes, this information is
provided in the form of assertions about other assertions, defining contexts
where assertions are valid. A recent extension to RDF which admits statements
over statements, called RDF-star, is in revision to become a W3C standard.
However, there is no proposal for a semantics of these RDF-star statements nor
a built-in facility to operate over them. In this paper, we propose a query
language for epistemic RDF-star metadata based on a four-valued logic, called
eSPARQL. Our proposed query language extends SPARQL-star, the query language
for RDF-star, with a new type of FROM clause to facilitate operating with
multiple and sometimes conflicting beliefs. We show that the proposed query
language can express four use case queries, including the following features:
(i) querying the belief of an individual, (ii) the aggregating of beliefs,
(iii) querying who is conflicting with somebody, and (iv) beliefs about beliefs
(i.e., nesting of beliefs).
