Guest Post (by Nick Lagos)

"The bane of my existence is doing things that I know the computer could do for me." -- Dan Connolly, The XML Revolution

In 1989, Tim Berners-Lee, a British researcher working at CERN (Conseil European pour la Recherche Nucleaire), envisioned the birth of a linked information system that would offer efficient access to data, regardless of the program or terminal in use. That led to the creation of the World Wide Web. Nowadays, the essential property of the World Wide Web is its universality. This constitutes both power and weakness, as anything can be found but the amount of information included is enormous and thus unmanageable. In order to confront the problem of information proliferation, changes have to be made to the current structure of the Web. Along these lines, Tim Berners-Lee proposed the reformation of the Web, as it exists, to the "Semantic Web". As Berners-Lee argues "the Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in co-operation the challenge of the Semantic Web, therefore, is to provide a language that expresses both data and rules for reasoning about the data and that allows rules from any existing knowledge-representation system to be exported onto the Web" (Berners-Lee et al. 2001).

So, the Semantic Web should provide enhanced information access based on the exploitation of machine-processable metadata. Facilities to put machine-understandable data on the Web are becoming a high priority for many communities. The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people. For the Web to scale, tomorrow's programs must be able to share and process data even when these programs have been designed totally independently. The Semantic Web is a vision: the idea of having data on the Web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications (W3C 2002).

But in order for the Semantic Web to become successful, it has to be based on the principles that made the current World Wide Web successful. According to Goble (2003) these are its scalability, by challenging assumptions on link consistency and completeness, and its simplicity. So the challenges that emerge for the semantic technologies to be brought in the Web are (Goble 2003):

  • The Web is vast, so solutions have to scale. Reasoning engines must perform quickly and robustly.
  • The Web is here--we have a legacy so we will have a mixed environment where some resources are "semantic" and some are just "Web". We must have a clear and achievable migration path from non-semantic to semantic.
  • The Web is democratic--all are knowledge acquisition experts and all are knowledge modellers. The barriers of admission must be low enough for most users to participate to the degree that is appropriate for them.
  • The Web grows from the bottom. Most people wrote their first HTML by editing a third parties. The Semantic Web will arise from fragments of metadata copied in a similar way.
  • The Web is volatile and changeable--resources appear and disappear, resources change.
  • The Web is dirty--there is no way to ensure consistency or whether information is trustworthy, and provenance is unknown. However, tolerance of error does not necessarily mean one should be oblivious to it.
  • The Web is heterogeneous--no one solution or one technology will be adopted; no one set of metadata will apply to a resource. Agreements are difficult, and mappings and translations will be common place.

Towards achieving the attainment of the Semantic Web, the development of three major technologies is needed. These are: a language that allows users to add structure into their documents easily and in a uniform way, a framework that would add meaning to the evolved structure and an entity that would solve the problem of communication. Each of these technologies will be presented and discussed in future sections.

Useful links: (W3C's page, the power behind the Semantic Web) (Community for the Semantic Web) (Example of a Semantic Web application) (Roadmap to the future for the Semantic Web) (Why Google marketplace became so successful?) (How can you make a semantic web site?)


  • W3C Semantic Web Homepage, (21 November 2002).
  • Goble, C. 2003. The Semantic Web: an evolution for a revolution. In: Computer Networks, Volume 42, Issue 5, pp. 551-556.
  • Berners-Lee, T.; Hendler, J. and Lasilla, O. 2001. The Semantic Web. Ed. Scientific American, Vol. 284, Issue 5, New York.