Given the sustained growth that we are experiencing in the number of SPARQL endpoints available, the need to be able to send federated SPARQL queries across these has also grown. To address this use case, the W3C SPARQL working group is defining a federation extension for SPARQL 1.1 which allows for combining graph patterns that can be evaluated over several endpoints within a single query. In this paper, we describe the syntax of that extension and formalize its semantics. Additionally, we describe how a query evaluation system can be implemented for that federation extension, describing some static optimization techniques and reusing a query engine used for data-intensive science, so as to deal with large amounts of intermediate and final results. Finally we carry out a series of experiments that show that our optimizations speed up the federated query evaluation process. ing complex queries by combining data from different, sometimes heterogeneous and often physically distributed datasets. SPARQL endpoints are RESTful services that accept queries over HTTP written in the SPARQL query language [1,2] adhering to the SPARQL protocol [3], as defined by the respective W3C recommendation documents. However, the current SPARQL recommendation has an important limitation in terms of defining and executing queries that span across distributed datasets, since it hides the physical distribution of data across endpoints, and has normally been used for querying isolated endpoints. Hence users willing to federate queries across a number of SPARQL endpoints have been forced to create ad-hoc extensions of the query language and protocol, to include additional information about data sources in the configuration of their SPARQL endpoint servers [4,5,6] or to devise engineering solutions where data from remote endpoints is copied into the endpoint being queried. Given the need to address these types of queries, the SPARQL working group has proposed a query federation extension for the upcoming SPARQL 1.1 language [7] which is now under discussion in order to generate a new W3C recommendation in the coming months.