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National Agricultural Library’s Linked Open Data Makes Connections in Agricultural Information

October 11, 2011

The National Agricultural Library’s (NAL) Agricultural Thesaurus is now available as Linked Open Data.

The NAL Agricultural Thesaurus (NALT) is used primarily to organize and describe agricultural information. It provides standard terms in both English and Spanish that can be used for indexing to improve the retrieval of information.

Linked Open Data translates information into a form both readable and understandable by computers. This translation makes it possible for different information resources, such as Web pages, datasets and research articles, to be interconnected at a level far beyond what we’re used to, creating meaningful relationships that make it easier to locate related content.

In other words, with the NALT now available as Linked Open Data, Web developers can use the NALT to specify the relationships between isolated data silos, thereby improving research into agricultural topics.

How does that happen? With the NALT available as Linked Open Data, NAL can now connect its vocabulary to other linked data vocabularies, such as AGROVOC, the multilingual agricultural vocabulary from the United Nations’ Food and Agriculture Organization. Once that connection is in place, the NALT, in turn, is connected to the web of connections AGROVOC has already made. Download Linked Open Data

For example, a search for "corn" in a database that uses the NALT retrieves items tagged with that term, as well as other items containing NALT’s specified synonyms, such as the English term "maize."

If, however, the NALT is connected to AGROVOC via Linked Open Data, then that one search for "corn" automatically returns items containing all the synonyms AGROVOC also includes, such as the terms "Mais" (the German equivalent) or "kukorica" (the Hungarian term). The Linked Open Data connection turns these two separate vocabularies functionally into one, and the researcher receives more related content as a result.

This example reflects the power of what has been called the "Semantic Web," as the computers themselves understand the meaning (i.e., the semantics) of the content and can then perform "intelligent" tasks for Web users—like connecting “maize” to all its synonyms and foreign language equivalents.

NAL’s move to openly share its thesaurus data with global web developers is offered in the spirit of the Open Government Directive to make government data publicly and freely available.

The NALT, produced annually since 2002, just celebrated its tenth edition in 2011. A Spanish version of the vocabulary has been available since 2007 and is cooperatively maintained by NAL and the Inter-American Institute for Cooperation on Agriculture. The data is used by a variety of government and private organizations to fulfill their need for a consistent and standardized terminology for agriculture and its supporting sciences. For more information, visit

NAL, one of four national libraries, holds one of the world's largest collections devoted to agriculture and related sciences. It is part of the Agricultural Research Service, U.S. Department of Agriculture, and is located in Beltsville, Maryland.

Last Modified: Oct 31, 2012
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Download the Thesaurus