What is STERNA?

Sterna Logo

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 field of natural science, biodiversity and conservation.

Birds and all kinds of information related to birds are at the core of the STERNA digital library. It brings together and presents all sorts of multimedia resources on birds, bird species and their habitats in one information space.


Currently, four prototypes of the search portal that access the STERNA information space are available:

Educational portal at ARKive

Birdwatchers' portal at NCB Naturalis

The Archipelagos search portal for tourists and boaters at sea

The Heritage Malta search portal for a generally interested audience


The name STERNA refers to the RNA project, where RNA stands for Reference Network Architecture. This project, supported by the Dutch ministries of Education and Economic Affairs, dealt with best practices for setting up dynamic knowledge systems. The STERNA project can be seen as the European follow up of the RNA project.


STERNA stands for Semantic Web-based Thematic European Reference Network Application.
  • Semantic: We use state-of-the-art semantic web technologies originally developed, proven and tested within the Dutch Reference Network Architecture project.
  • Web-based: STERNA is a web-based application to increase and improve access to heterogenous resources on the Internet. Yet, rather than building a central repository of resources, it connects and links digital content that remains within the original databases.
  • Thematic: The resources presented in this digital library focus on a common theme: birds. The information space brings 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 outstretches the possibilities of the project to translate resources at the level of single content items, through the use of multilingual reference structures, multilinguality is achieved at the object description level: Users are able to issue a query in their native language and will receive relevant resources from many different participating members.
  • Reference structures: They constitute the actual "glue" between the resources and are used to search and retrieve content items that are semantically related. Under the term reference structure 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. 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 allow 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 used in STERNA:

Sterna architecture: federated and member sites


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 are the benefits 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.



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What are the benefits 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, 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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The STERNA project is supported and partly funded by the eContentplus programme of the European Commission.

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