The School of Web Semantics Learning Semantic Web Techniques

In October last year (at the Polish edition of the School of Semantics), I introduced the lightweight ontology called Dublin Core. It is one of the oldest and probably the most popular ontologies used not only in Web 3.0, but all across the Web. Did you know that the Dublin Core standard comes from the digital libraries domain? Another ontology that is closely related to digital libraries is SKOS (which I also wrote about last year).

These ontologies and other standards arose from digital libraries research. Many of the ideas that formed the foundations for the Semantic Web come directly from the digital libraries domain; many people closely associated with the development of Web 3.0 also have some experience working with digital libraries. So you may be surprised to learn that until only recently these two research domains, i.e., digital libraries and the Semantic Web, could not find a common language.

When we think of a library, two pictures come to mind: a collection of books and a building where these books are stored. However, it is more difficult to define the concept of a digital library:

• Are digital libraries simply directories (available via the Internet) to search  library resources  (called Online Public Access Catalog - OPAC)?
• Or, is a digital library a collection of scanned documents, such as antique books, published on the Internet?
• Or maybe, a digital library is a collection of resources and metadata available through the web browser?
• Finally, perhaps a digital library is a computer system for publishing collections of resources on the Internet?

In addition, digital libraries can be considered both in historical and technological terms. We also take into account the different aspects of their operation: cataloging, information management, information retrieval and user interaction. As you can see the answer to this question (What is a digital library?) is not trivial. One of the European projects on digital libraries, DELOS (now dl.org), delivered a report that attempts answers this and other questions. I will discuss some of them in the following articles in the "Semantic Digital Libraries" series.

As previously mentioned, research on digital libraries delivered a number of standards that are now quite commonly used on the Internet. But until recently the same digital libraries have not really been a part of the Web. They offer services which are often incompatible among themselves not to mention other Internet services. What is more, not so long ago, digital libraries completely rejected social media or any other unsupervised addition of new content or metadata. Additionally, controlled vocabularies (such as thesauri and taxonomies) maintained and used by digital libraries are usually not updated often enough to reflect the current state of knowledge. We should also point out that the user experience provided by digital library systems often differs significantly from that known from other popular web services, like Facebook or Twitter; hence digital libraries often do not meet the needs and expectations of the Internet users, especially of younger generations.

Research on semantic digital libraries aims to achieve better integration between services offered by digital libraries and other services on the Internet, and to improve the user experience provided by digital libraries.

Semantic digital libraries combine results from three research domains:

• Digital libraries deliver knowledge organization systems, dictionaries, thesauri, classification systems, etc.
• The Semantic Web provides solutions for extending current (bibliographic) descriptions and interoperability with other metadata standards and services on the Internet.
• Web 2.0 introduces social descriptions of resources (tagging) and communities of library users.

You may have heard about the initiative called Library 2.0. Some of the ideas regarding semantic digital libraries are similar to the concept of Library 2.0, which is based on 5 elements: open-source, single sign-on (or shared authentication), open standards, integrated OPACs, and of course social media. However, Library 2.0 lacks two essential elements: semantic solutions to ensure extensibility and interoperability, and relations to Web standards and services. Library 2.0 is very popular at the moment, however, in my opinion, we should refrain from saying that digital library systems that allow tagging are semantic digital library systems; there is a whole lot that those systems do not provide.

To sum up this article, I would like to briefly mention a few projects that are strongly related to the idea of semantic digital libraries. In the following weeks I try to describe them a little more closely.

• DuraSpace started last year as a joint initiative of two communities: a popular digital library system DSpace and Fedora Commons providing the infrastructure to build powerful and rich functionality of semantic digital libraries.
• JeromeDL is a project run by DERI Galway and Gdansk University of Technology, with commercial support from Knowledge Hives. It is based on Elvis-DL, a prototype of  a semantic digital library that I created at the Gdansk University of Technology in 2003. Along with JeromeDL we delivered several other projects (within the cluster project Corrib.org), including, among others, the MarcOnt Initiative that provides services, components and ontologies for semantic digital libraries.
• Greenstone is another very popular open source digital library system that enables, among others, effective use of geolocation information.
• SIMILE is a project run by the MIT Libraries; it provides a number of components enabling easy conversion of a classical digital library (or any other web site) into an interactive, feature-rich service based on semantic technologies.
• BRICKS project was conducted under the EU Sixth Framework Program (FP6); it provided a number of components and an infrastructure that enabled social and semantic annotations on library resources and supported exchange of concepts between digital library systems.

You can learn more about Semantic Digital Libraries at the dedicated site of this initiative; you will find there several presentations (including half-day and full-day tutorials) and descriptions of two books on the subject.

Translated by Sebastian Kruk and Jodi Schneider