Tuesday, March 23, 2010

SPARQL Based Navigation of RDFa Encoded Named Entities

This is a quick heads up on a new feature at Nomisma.org, the ANS-hosted project assigning stable URIs to numismatic concepts.

At http://nomisma.org/id/lyttus you'll find a very brief representation of the ancient site of Lyttus in Crete. It links to the relevant Wikipedia article and Barrington Atlas ID so it should be unambiguous which site we mean and it should be easy to find out further information. As a convenience, and to make it easy to put a dot on the map, the page also has latlong info.

This post is about the list of URIs prefaced by the text "The following Nomisma IDs refer to this ID:". If you click on http://nomisma.org/id/igch0151, you'll get a description of a hoard of coins as published in Inventory of Greek Coin Hoards.

Nomisma.org uses RDFa so the markup of the hoard includes the snippet: <span rel="nm:mint" resource="lyttus">Lyttus: 1 dr.</span> . You can click on "Show Markup in Page" to see this.

All the descriptions of numismatic concepts are collected in a single RDFa file at http://nomisma.org/nomisma.org.xml and as RDF-XML at http://nomisma.org/nomisma.org.rdf. That one snippet from igch0151 will produce the triple:

So... visiting http://nomisma.org/id/lyttus queries http://nomisma.org.rdf with a SPARQL statement of the form ' SELECT ?id WHERE { ?id ?refersto <http://nomisma.org/id/lyttus> }'. This just binds "?id" to a list of the ids that refer to Lyttus.

Bottom line: Simple markup achieves meaningful results using pre-existing standards. I wrote none of the tools to make this work. It will be fun when I get around to turning that list of IDs into a map, which will be simple using the Google Maps API. Then we will have a geographic front-end to "SPARQL-based Navigation of RDFa Encoded Named Entities".

Note: all of the RDFa patterns are in the process of being defined and the entries are in the process of being markedup. I.e., this is all in alpha stage.

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