The Semantic Web provides a common framework that allows data to be shared and reused across application, enterprise, and community boundaries. It is a collaborative effort led by W3C with participation from a large number of researchers and industrial partners. It is based on the Resource Description Framework (RDF).

Here the following tools of Semantic Web:

Jena
Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.

Jena is open source and grown out of work with the HP Labs Semantic Web Programme.

The Jena Framework includes:
A RDF API
Reading and writing RDF in RDF/XML, N3 and N-Triples
An OWL API
In-memory and persistent storage
SPARQL query engine

Homepage: http://jena.sourceforge.net/
Download: Jena 2.5.6


ARC
ARC is a flexible RDF system for semantic web and PHP practitioners.
It's free, open-source, easy to use, and runs in most web server environments.

ARC is easy to bundle with existing PHP/MySQL software
-Works with PHP4 and PHP5
-No use of global variables, constants, or other practices which may cause integration problems
-Error collection, avoidance of PHP warnings and notices
-Automatic path detection for component inclusion
-Components are kept as small as possible, only immediately required code is loaded into memory
-Customizable per-store prefix for database tables

Homepage: http://arc.semsol.org/
Download: ARC 2 2008-07-01: ZIP file (100KB)
Requirements: PHP 4.3 or higher / MySQL 4.0.4 or higher

Sesame
Sesame is an open source RDF framework with support for RDF Schema inferencing and querying. Originally, it was developed by Aduna (then known as Aidministrator) as a research prototype for the EU research project On-To-Knowledge. Now, it is further developed and maintained by Aduna in cooperation with NLnet Foundation, developers from Ontotext, and a number of volunteer developers who contribute ideas, bug reports and fixes.

Homepage: http://www.openrdf.org/
Download: Sesame 2.2-beta2

OWL API
The OWL API is a Java interface and implementation for the W3C Web Ontology Language OWL. The latest version of the API is focused towards OWL 2.0 which encompasses, OWL-Lite, OWL-DL and some elements of OWL-Full.

The OWL API includes the following components:
An API for OWL 2 and an efficient in-memory reference implementation
RDF/XML parser and writer
OWL/XML parser and writer
OWL Functional Syntax parser and writer
Turtle parser and writer
KRSS parser
OBO Flat file format parser
Support for integration with reasoners such as Pellet and FaCT++
Support for black-box debugging


Homepage: http://owlapi.sourceforge.net/
Download: binary release (2.2.0) - 17th April 2008


Topaz
Topaz is a powerful object to RDF persistence and query service. Based loosely on the ORM family of software, Topaz lets you develop persistent classes following object-oriented concepts such as inheritance, composition, association, etc. Besides allowing use of the underlying RDF store's native query language, Topaz provides its own language (OQL), which applications can utilize to query based on defined objects. Topaz is written in Java and is available under the ECL till 0.8.3 and Apache open source license for subsequent releases.


Homepage: http://www.topazproject.org/trac/