Vocabularies in the VO

There are multiple vocabularies and thesauri within astronomy, of which the best known are the 1993 iau Thesaurus and the keyword list main- tained by A&A, ApJ and MNRAS. The ivoa has agreed a standard for publish- ing vocabularies, based on the W3C skos standard, to allow greater automated interaction with them, in particular on the Web. This allows links with the Semantic Web and looks forward to richer applications using the technologies of that domain. Vocabulary aware applications can benet from improvements in both precision and recall when searching for bibliographic or science data, and lightweight intelligent ltering for services such as VOEvent streams. In this paper we present two applications, the Vocabulary Explorer and its companion the Mapping Editor, which have been developed to support the use of vocabularies in the Virtual Observatory. These combine Semantic Web and Information Retrieval technologies to (i) illustrate the way in which formal vocabularies might be used in a practical application, (ii) provide an online service which will allow astronomers to explore and relate existing vocabularies, and (iii) provide a service which translates free text user queries into vocabulary terms.