From the website:
The goal of Ordnance Survey’s GeoSemantics team is to provide both an explicit representation of our organisation's knowledge and a set of increasingly automated operations that allow different datasets to be combined together, by representing them in a semantically meaningful way via ontologies. Ontologies contain a set of knowledge about a domain, such as topography.
We are building a Topographic ontology, a staged process where we are building ontologies of the sub-domains within topography. These are updated as we learn more about ontology authoring, so the latest versions can be found here, while previous versions are still available for backwards compatability. So far we have built ontologies describing Hydrology, Buildings and Places and Administrative Geography, along with modules that contain terms in common. The Administrative Geography ontology also includes RDF triple data.
