Redland RDF Application Framework - Java Interface

Redland Java interface

This is built if --with-java is given to the configure line, or --with-java=java to use a particular Java version/program.

The --with-jdk configure argument MUST be given give the location of the root of the full JDK installation so that the interface can be properly compiled against the correct Java Native Interface (JNI) headers for the JDK that provides the java program.

The standard 'make' at the top level will build it once enabled as above. You can also compile the Java interface by hand as follows:

  cd java
  make

  # optional, but it may require a top-level 'make install
  # first depending on the operating system and how it
  # handles shared libraries
  make check

(the make check may fail without the files being installed)

To install it system wide do this as root (or maybe via sudo make install):

  root# make install

which will copy the librdf-java.jar to PREFIX/share/java and the shared library librdf-java.so to PREFIX/lib. This is not a standard location between systems so might have to be done by hand.

The Redland Java interface is beta quality - the object based API is present but not been used extensively. The API has been has been tested with the following versions:

1.2.1 on Solaris/Sparc
1.4.1 on OSX/PPC
1.4.1_01 on Linux/x86
1.4.2 on Linux/x86
1.4.2-p5 on FreeBSD/x86

The JNI header and library files are in different places on all systems so the --with-jdk may need to be used to give the location of the root of the full JDK installation if it cannot be found by the paths that the configure program knows of. This should then find the JNI header files in the include and include/system sub-directories (such as "solaris" or "linux").

Testing the Redland Java interface

There is the beginnings of an example program in example.java which is mostly for reading (along with the test1.java) but can be compiled and run with:

  make example

which tries to set the shared library path for librdf-java.so

Redland Java API Introduction

The Java API is an object-based API reflecting the same structure of the Redland objects with simple mappings between them:

Concept	Redland Class	Java Class	Purpose
Resource / Literal	librdf_node	`org.librdf.redland.Node`	RDF Model & Syntax nodes
Statement / Triple	librdf_statement	`org.librdf.redland.Statement`	RDF Model & Syntax arcs (statements, triples) [isa Resource]
Model	librdf_model	`org.librdf.redland.Model`	Set of Statements usually held in one Storage.
Storage	librdf_storage	`org.librdf.redland.Storage`	Storage for Models either persistant or in-memory.
Stream	librdf_stream	`org.librdf.redland.Stream`	Providing sequences of Statements from Parsers, queries.
Parser	librdf_parser	`org.librdf.redland.Parser`	Syntax parsers delivering Stream of Statements or writing to a Model
Serializer	librdf_serializer	`org.librdf.redland.Serializer`	Serialize Models into various syntaxes such as RDF/XML.
Iterator	librdf_iterator	`org.librdf.redland.Iterator`	Enumerating lists (of Node) from queries.
URI	librdf_uri	`org.librdf.redland.URI`	Provides URIs for Resources, Parsers, ...
World		`org.librdf.redland.World`	RDF wrapper class handling Redland startup/shutdown
Digest	librdf_digest		Internal content digest class
Hash	librdf_hash		Internal key:value maps class
List	librdf_list		Internal list class

Other RDF Java APIs and applications

The follow are useful pure-Java applications (no C library)

Jena Semantic Web Toolkit by the HP Labs Semantic Web group, Bristol, UK. Originally started by Brian McBride.
ARP: Another RDF Parser, by Jeremy Carroll, HP Labs. Now part of Jena.
Sesame which provides an architecture for persistent storage and querying of RDF and RDF Schema, using an RDF Schema Query Language (RQL). Developed by aidministrator and OntoText.
KAON open-source ontology management infrastructure based on the J2EE Java Beans framework. Developed by FZI / AIFB, University of Karlsruhe