Linked Data Fragments Server

On today's Web, Linked Data is published in different ways, which include data dumps, subject pages, and results of SPARQL queries. We call each such part a Linked Data Fragment.

The issue with the current Linked Data Fragments is that they are either so powerful that their servers suffer from low availability rates (as is the case with SPARQL), or either don't allow efficient querying.

Instead, this server offers Triple Pattern Fragments. Each Triple Pattern Fragment offers:

• data that corresponds to a triple pattern (example).
• metadata that consists of the (approximate) total triple count (example).
• controls that lead to all other fragments of the same dataset (example).

This is a Java implementation based on Jena.

Build

Execute the following command to create a WAR and JAR file:

$ mvn install

Deploy stand alone

The server can run with Jetty from a single jar as follows:

java -jar ldf-server.jar [config.json]

The config.json parameters is optional and is default the config-example.json file in the same directory as ldf-server.jar.

Deploy on an application server

Use an application server such as Tomcat to deploy the WAR file.

Create an config.json configuration file with the data sources (analogous to the example file) and add the following init parameter to web.xml:

<init-param>
  <param-name>configFile</param-name>
  <param-value>path/to/config/file</param-value>
</init-param>

If no parameter is set, it looks for a default config-example.json in the folder of the deployed WAR file.

Status

This software is still under development. It currently supports:

• HDT & Jena TDB data sources
• HTML, Turtle, NTriples, JsonLD, RDF/XML output

A more complete server has been implemented for the Node.js platform.