RDFDot

Tools for drawing graphs from RDF files with GraphViz implemented in Java 8 using Java Native Interface calls to GraphViz.

Demo

You can access the demo at our demo server, it should be running most of the time. Simply cut & paste a Turtle or RDF/XML document, optionally change the configuration and press "Render".

Building

RDFDot comes with several different renderers for accessing the Graphviz layouting library. There are two different approaches:

• call the dot process as external shell command from Java; requires graphviz to be installed and accessible on your server
• use the Java Native Interface library that is provided by RDFDot; faster but requires manual compilation

External Shell Command

The first approach is simple to build using standard Maven:

mvn clean install -DskipTests

The -DskipTests is necessary at the moment, because some tests require the JNI library to work properly.

Java Native Interface

If you want to use the JNI library, please follow the following sequence:

mvn clean
cd rdfdot-core/src/main/native
make
cd ../../../..
mvn install

Calling make will download all the necessary C libraries, compile them and link them statically into a JNI library for RDFdot. Note that this has only been tested to work on Linux.

Installing

RDFDot currently consists of the libraries rdfdot-api and rdfdot-core, which you can use in your own projects, and the web application rdfdot-web, which can be deployed in any Java web container. When RDFDot has been properly installed, simply add the approprate Maven dependencies to your project:

<dependency>
    <groupId>net.wastl.rdfdot</groupId>
    <artifactId>rdfdot-core</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</dependency>

If you want to use the (faster) JNI rendering library, it is necessary that you copy the libgraphviz.so library to an appropriate location and call Java with -Djava.library.path=/path/to/location.

Library Usage

Configuration

The rdfdot-api library contains a class GraphConfiguration, which can be used for setting layouting configuration options for the graph. It currently supports changing the node style, shape, color, and fillcolor for URI, BNode and Literal nodes, as well as the arrow shape, style and color for edges. Furthermore, it is possible to change the layout direction of the graph (default: left-right). All available options are defined using the enums Arrows, Layouts, Shapes and Styles.

RDFHandler

The visualization library is implemented as a Sesame RDFHandler, so it can be used anywhere Sesame accepts an RDFHandler, e.g.

• in a RIO parser (using RDFParser.setRDFHandler(...))
• in a repository query (using RepositoryConnection.exportStatements(...))
• in a SPARQL graph query (using GraphQuery.evaluate(...))

To initialize the RDFHandler, use e.g. the following sequence of statements:

    GraphConfiguration configuration = new GraphConfiguration();
    GraphvizSerializer serializer = new GraphvizSerializerNative(configuration);

    RDFParser parser = Rio.createParser(RDFFormat.TURTLE);
    parser.setRDFHandler(new GraphvizHandler(serializer));
    parser.parse(in, "http://localhost/");

    byte[] image = serializer.getResult();

Different GraphSerializers are available, including GraphSerializerNative (using JNI calls) and GraphSerializerCommand (executing a shell command).