FedX Short Documentation

FedX is a practical framework for transparent access to Linked Data sources through a federation. It incorporates new sophisticated optimization techniques combined with effective variants of existing techniques and is thus a highly scalable solution for practical federated query processing.

Core Features

• Virtual Integration of heterogeneous Linked Data sources (e.g. as SPARQL endpoints)
• Transparent access to data sources through a federation
• Efficient query processing in federated environments
• On-demand federation setup at query time
• Fast and effective query execution due to new optimization techniques for federated setups
• Practical applicability & easy integration as a Sesame SAIL
• Comprehensive CLI for federated query processing from the command line

Getting Started

Refer to Getting Started.

System overview

FedX is built on top of RDF4J and constitutes a practical federation layer as a RDF4J SAIL implementation. It allows to virtually integrate Linked Data sources using any RDF4J SAIL mediator (e.g. as SPARQL endpoint or NativeStore) and the (virtually) combined RDF graph of those sources can be used or federated query processing. In contrast to the SPARQL 1.1 Federation Extensions our system allows for transparent integration of data sources, meaning that sources do not have to be stated explicitly in the query. FedX incorporates the following optimization techniques to allow for efficient query processing in a distributed setting:

• Statement sources: Examine relevant statement sources using SPARQL ASK queries
• Join order: Join reordering using variable counting technique & heuristics
• Bound joins: Compute joins as block nested loop
• Exclusive groups: Group statements with same relevant source

Details to the optimization techniques can be found in our publication. All of our optimization techniques use SPARQL 1.0 Features only, making our solution suitable in contemporary environments. Still the SPARQL 1.1 language features are supported. Note that our system does not need any preprocessed metadata such as statistics or indices making it suitable for on-demand query processing. In particular, FedX is designed to work as an out-of-the box system.

License Information

FedX is licensed under the Apache License 2.0 for use in open source applications.