Sesame

storage and querying middleware for the Semantic Web

The Semantic Web

In his book Weaving the Web, Tim Berners-Lee talks about the vision that inspired him to invent the World Wide Web. Although the Web as we know it today has already changed everyday life, facilitating communication between people all over the world as if they were each other'ss neighbours, Tim Berners-Lee's vision has yet to be fulfilled. The Web, as he saw it, included machines communicating with people and with each other, rather than people just using machines to talk to one another. He calls this web The Semantic Web.

The Semantic Web is about the meaning of information, whereas the current World Wide Web is only about the information itself. For machines to be able to communicate with each other and with people, they will need a common understanding of what information means. For this, machine processable meta-information -- information about the information -- is needed.

The World Wide Web Consortium, founded by Tim Berners-Lee, has been working on (and still works on) standards for defining this machine processable meta-information. The now omnipresent language XML was the first step. The next step was the definition of RDF (Resource Description Format), a format that allows you to define anything about everything and that uses XML as an interchange syntax.

Next steps include the definition of languages for modelling information so that it becomes machine understandable. First inroads in this direction have been made with RDF Schema, OIL and DAML+OIL, languages which will serve as important input to the new Web-Ontology Working Group.

Sesame

Sesame is a software program that was originally developed in the IST-project On-To-Knowledge, which also produced the OIL language. In this project, a storage and querying service for RDF and RDF Schema was developed. This software was baptized Sesame.

The most important features of Sesame are:

Scalability

Sesame has been designed with scalability as its primary focus. By design, it is able to scale from handhelds to powerful enterprise servers.

Powerful query language

The supported query language RQL is the only language of its kind, offering native support for RDF Schema semantics.

Portability

Sesame is written completely in Java, allowing it to be run on all mainstream platforms.

Repository independence

Sesame abstracts from the actual repository being used for storing data. This allows Sesame to be run on top of any DBMS, or even on completely different kinds of repositories.

Extensibility

Sesame's architecture allows for other functional modules to be plugged in, thus adding new functionality to the program.

Flexible communication

The architecture separates the communication details from the actual functionality through the use of protocol handlers. Supporting other communication protocols is only a matter of adding the appropriate protocol handler.

As the amount of available meta-data grows, the need for a scalable repository and accompanying querying service will arise. Being able to offer this, Sesame has the potential to become an important building block of the Semantic Web. The flexibility and openness of Sesame's architecture will allow it to be integrated in a wide variety of applications.