I’ve been travelling overmuch for the last six weeks, but met lots of lovely people. Most recently, during a trip this week to discuss the Open Knowledge Foundation‘s part in the LOD2 consortium project, had a long chat with Jens and Claus, the developers and academics behind Linked Geo Data, the Linked Data version of the OpenStreetmap data.
The most interesting bit for Unlock is the RESTful interface to search the data; by point, radius, and bounding box, by feature class and by contents of labels assembled from tags. So it looks like Opensearch Geo as much as Unlock’s place search api does.
Claus made up a mapping between tags and clusters of tags in OpenStreetmap, to a simple linkedgeodata.org ontology. Here’s the mapping file – warning, it is quite large – OSM->linkedgeodata mapping rules. Pointed him at Jochen Topf’s new work on OSM tag analysis and clustering, Taginfo.
As well as the REST interface, there is a basic GeoSPARQL endpoint using Virtuoso as a Linked Data store – we ran containment queries for polygons returning polygons with reasonable performance. There is a fracturing in the GeoSPARQL world both in proposed standards and in actual implementation.
So we want to be able to return links to LinkedGeodata.org URLs in the results of our search. Right now Unlock’s place search returns original source identifiers (from geonames, etc) as well as our local identifiers, for place-names and shapes. In fact Unlock could help with the mapping across of Linkedgeodata.org URLs to geonames URLs, which are quite widely used, an entry point into the bigger Linked Data web.
Another very interesting tool for making links between things on the Linked Data web is SILK, by Chris Bizer, Anja Jentsch and their research group at the Freie Universitat Berlin. The latest (or still testing?) release of SILK has some spatial inference capacity as well as structural inference. So we could try it out on, for example, the Chalice data just to see what kind of links can be made between URLs for linkedgeodata things and URLs for historic place-names.
We’ve been setting up an instance of OpenStreetmap for Unlock and other purposes at EDINA recently. Our plan with this is to start working from Nominatim, which has a point-based gazetteer for place-names down to street address level, and attempt to extract and/or generalise shapes as well as points corresponding to the names. We’re doing this to provide more/richer data search, rather than republishing original datasets in some more/differently interpretable form. So there’s lots of common ground and I hope to find ways to work together in future to make sure we complement and don’t duplicate.