Wednesday 1 August 2012

Pelagios WP2 at Glance: Discovery Services

Whereas WP1 shows how Pelagios RDF annotations can be discovered, aggregated and served via a basic API, WP2 focused on the specifically spatial elements of what we were doing. In particular, our goals were to:
  1. develop services to provide ranked, relevant materials based on input of place URIs and Named Entities or spatial coordinates.
  2. provide super users with specific APIs that permit them to perform federated place- and space-based queries over the resources catalogued by WP1.
  3. enrich results with additional data from sources such as GeoNames, DBpedia and Freebase, returned in a variety of optional Web formats (RDF, JSON, KML, Atom)

In order to achieve these Rainer extended the standard API so that, in addition to returning annotations associated with a single resources, those from multiple places within a co-ordinate bounding box could be returnedThis is very useful for instances in which the relevant coordinates are known, but users are often interested in mereological (part-whole) relationships: returning annotations for all the places in Latium, for example. To accomplish this, Gianluca made use of the online spatial database CartoDB and a shape file of Roman provinces kindly provided the DARMC project. This allows us to create performant spatial queries by first requesting annotations from the Pelagios API filtered by a bounding box, and then filtering it a second time again against a regional polygon.

The principle difficulty encountered with this approach is one of data granularity. We only have approximate boundaries for Roman provinces most of the time, and these are fluid over time. Indeed, in many cases boundaries in Antiquity were only ever approximately defined in the first place. While better polygon datasets will certainly help us with coarse-grained queries, we will need to accept that any such results must be considered provisional at best and should be subjected to further scrutiny. One long term aim may be to create RDF associations between places and their regional affiliations which can remain spatially independent.

We had originally intended to automatically provide additional content associated with GeoNames, Wikipedia and Freebase, but it later occurred to us that this goes against the grain of Pelagios. These are resources just like all our other partners and it makes sense to treat them as such. As a result, we are converting Pleiades+ into an RDF annotation of GeoNames resources, (and where available, wikipedia and Freebase) that can be incorporated directly through the Pelagios API. These will come online in early August.

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