Vocabularies
Contents
Controlled Vocabularies
Vocabularies are a mechanism to formalise the terminology used within a domain of discourse and the semantic relationships between those terms. Typically, a vocabulary is developed to (i) limit the available terms used and (ii) provide consensus on the meaning of the terms.
SKOS is a W3C Proposed Recommendation for publishing and sharing vocabularies on the Semantic Web. A SKOS document captures the information of a vocabulary as RDF statements.
Astronomy Vocabularies
Within the field of astronomy there are many existing vocabularies which have been developed for different purposes by different organisations. These are summaries in the table below. The one exception is the IVOA Thesaurus which is being developed as an updated version of the IAU Thesaurus.
| Vocabulary Name | Publisher | Purpose | Size | SKOS Version |
|---|---|---|---|---|
| Astronomy Visualization Metadata(AVM ) | IVOA | A taxonomy of metadata for tagging images to enable efficient retrieval for outreach purposes. | 200-300 terms | AVM |
| Astronomy and Astrophysics Journal keywords (A&A) | A&A | A set of keywords used for tagging journal articles to summarise their content. | 200-300 terms | A&A |
| International Astronomical Union thesaurus (IAU Thesaurus) | IAU | A thesaurus of astronomical terms published in 1993. (Has not been updated since.) | 2,500 terms | IAUT |
| International Virtual Observatory Alliance Thesaurus (IVOAT) | IVOA | An update of the IAU Thesaurus. | ~3,000 terms | IVOAT |
| Universal content descriptors (UCD) | IVOA | Tags for describing the content of a column in a relational database. | 200 terms | UCD |
As part of the IVOA effort to enable the use of vocabularies within the virtual observatory, we have been involved with developing
- Standards for publishing astronomical vocabularies using SKOS (a semantic web standard for publishing machine processable vocabularies)
- SKOS versions of the existing vocabularies
- An update of the international astronomical union thesaurus
- Techniques for relating the terms in the various vocabularies.
These have now been published as an IVOA Proposed Recommendation.
Vocabulary Tools
As part of our effort to help enable the use of vocabularies within the virtual observatory, we have developed three applications for SKOS encoded vocabularies.
Vocabulary Explorer
The Vocabulary Explorer allows a user to discover details about the terms used within a vocabulary, and their relationship to other terms both in the same vocabulary and across vocabularies. To enable the relationship to terms in other vocabularies, mapping files relating the terms in two vocabularies are required. At present, the vocabulary explorer only knows about one such mapping file, linking the astronomy and astrophysics journal keywords to the astronomy visualization metadata taxonomy.
Suggestion Server
The Suggestion Server is an XML-RPC services that offers a limited subset of the functionality of the Vocabulary Explorer. It relies on the same search modules as the Vocabulary Explorer. More details of the location of the service and the available functions can be found on the support page.
A typical interaction with the service would be:
- Search for vocabulary concept URIs that match some query
- Get the preferred label for a selected URI
Mapping Editor
The Mapping Editor is a Java application that provides a graphical user interface to enable a user to declare mappings between two vocabularies. Below are three screenshots showing how vocabularies are loaded into the application, and how mappings are expressed. The mapping editor enables the mapping document to be saved as either rdf/xml or turtle notation. Additionally, an existing mapping file can be loaded in and edited.
