STERNA (Semantic Web-based Thematic European Reference Network Application) is a Best Practice Network project supporting the objectives of the European Digital Library by pioneering the integration of semantically enriched digital resources in the natural sciences and history field.

• What's in the name?
• How does it work?
• What's the benefit for users?
• What's the benefit for content providers?

What's in the name?

Sterna is a genus of TERNS (therefore our logo!) in the bird family Sternidae. While it used to encompass most "white" terns indiscriminately, it is now restricted to the typical large white terns occurring near-globally in coastal regions. (Source: Wikipedia)

Birds and all kinds of information related to birds will also be at the core of the to-be-built STERNA digital library. A first prototype of this information space, presenting and bringing together all sorts of multimedia resources on birds, bird species and their habitats will be available to the public in December 2009.

In the context of this project, STERNA stands for Semantic Web-based Thematic European Reference Network Application.

• Thematic: The resources presented in this to-be-built digital library focus on a common theme: birds. The information space will bring together all sorts of information on birds, their habitats, and other bird-related topics such as bird-flu, migrating birds or different bird species.

• European: Linking digital libraries all over Europe implies to become multilingual. Although it will outstretch the possibilities of the project to translate resources at the level of single content items, through the use of multilingual reference structures, multilinguality will be achieved at the object description level: While users will be able to issue a query in their native language, they will receive relevant resources from many different participating members.

• Reference structures: They constitute the actual "glue" between the resources and will be used to search and retrieve content items that are semantically related. Under the term reference structures we subsume all sorts of "controlled vocabulary", from simple word lists and glossaries to taxonomies, thesauri and ontologies. By sharing and connecting reference structures into a coherent network of concepts, and then attaching digital resources to this global reference network, geographically dispersed content items can be searched and retrieved from any of the member sites.

• Network: STERNA is a network of independent, autonomous member institutions. Joining STERNA means to provide access to the institution's metadata which is stored not in a central repository but at the participating member sites. Thus institutional work flows and information structures remain intact and will not be altered when contributing to the distributed digital library.

• Application: STERNA is a web-based application that can be accessed by users via the member sites. It is based on a "software as a service" concept, meaning that one core site provides services to the affiliated member sites on request.

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How does it work?

STERNA utilises state-of-the-art semantic web technologies which have been developed, proven and tested in the RNA project (http://www.rnaproject.org). The basic architecture allows distributed querying of content at member sites based on metadata in RDF (Resource Description Framework) format and/or reference structures represented in SKOS (Simple Knowledge Organisation System) format.

In addition, content holding institutions can rely on a set of web-based tools and data mining procedures to semantically enrich their content (manually adding or automatically extracting metadata) and additional web-based tools to link and integrate their collections and content items with the digital resources of other providers via their reference structures.

Finally, users can utilise a set of tools implemented as software as a service that allows them to search across collections and also to contribute and enrich their own content, while providing convenient site features like facet navigation to improve their searches.

The following graphic depicts the basic functioning of the distributed digital library architecture that will be implemented in STERNA:

Distributed querying is made possible as a federated functionality. This means that the necessary technology (query analyser) and data to support distributed querying is provided only by one member site (the federated site D), while the other participating members of the network allow partial and controlled sharing of their data.

Users may initiate their query at any of the member sites (sites A, B, C, or D). The query is then routed to the federated site (site D) where it is resolved into its fundamental parts, and then intelligently routed to the relevant member sites. The query analyser then collects and integrates the responses into a result list, which is sent back to the user at the member site where the query originated.

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What's the benefit for users?

• Users can carry out searches across all the participating member sites simultaneously, thus making searches more effective and transparent.

• Search results become more relevant as the number of results returned is limited. The list contains only those content items that have been semantically connected via their reference structures.

• Users can start queries based on general concepts and do not necessarily need to know the accurate expert term or classification system to discover relevant content. Thus, laypersons and non-expert users gain access to content normally reserved to experts.

• Applying advanced navigation tools such as facet navigation, STERNA supports users in browsing and navigating through relevant web content.

• Finally, users will be able to actively contribute to the digital library by allowing them to enrich and contribute their own content.

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What's the benefit for content providers?

STERNA specifically addresses small content organisations that do not have the financial resources or the technical skills to participate in the European Digital Library initiative. STERNA, through its software as a service concept, offers them the possibility to actively contribute content to a digital library by providing a simple and proven technological architecture that does not call for institutions to become technical experts themselves.

The proposed architecture also supports content organisations that favour the idea of institutional flexibility and autonomy. As members of the network, they decide on partial and controlled sharing of their data, while local information structures and systems are left intact and digital resources remain within their databases.

As members of the STERNA network, however, they may benefit in various ways:

• By integrating their digital resources with the resources of the other network members via reference structures, they can quickly achieve a critical mass of content which may attract new users.

• As reference structures in many different languages are linked into a global reference structure network, non-native users will be able to retrieve relevant information resources in various languages, thus opening up collections to a wider, international audience.

• STERNA also offers users access to a set of tools that will help them to add and semantically enrich their own content to a comprehensive digital library. 

• Finally, content providers will also be able to better leverage their investment in content digitisation, by sharing and integrating their resources into a greater network.

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