ACTION-15 - Review requirements for use case 16

Hi everyone,

The following requirements are listed for use case 16 (Combining spatial 
RDF data for integrated querying in a triplestore):

  * URIs
  * There should be standards that allow data sources (data sets or data
    services) to describe their spatial characteristics (like number of
    dimensions, data type (raster or vector), CRSs, spatial extent,
    spatial resolution).
  * There should be a common encoding/serialisation for spatial data as RDF
  * There should be a standard for publishing data about coordinate
    reference systems  (CRS) - Not only geographical reference systems.
  * There should be a default CRS that is assumed when no CRS is specified

These requirements are sufficient for use case 16.

Thanks,
Matt