add entity types

[valevo]

background

• use case: all RGs with the geographical tag "Indonesia" constitute the cluster of RGs on Indonesia
  -> eventually, you'd want an RG on Indonesia itself and that RG as the introduction document for this cluster of RGs
  -> this can be matched via the "Identifier" field of a RG (i.e. the geonames URI for the Indonesia RG will match the geographical tag URI in other RGs) but perhaps we need extra information in the RG on Indonesia

TODO

• add "entity type" tags to RGs, e.g. something like "Geographical Entity", "Geopolitical Entity", "Person", etc.
  -> in the example above, the info "Geographical Entity" as entity type + the geonames link of the RG for Indonesia is sufficient to automatically make the necessary connections

Questions

• other uses?
• controlled vocabulary? which set of entity types do we draw from?

[wreints]

I think this is a good idea. Do you know any sets of entity types that we can use? Should not be much work to add these to the RG's!

[valevo]

see #16 for another way to address this (that might be easier to model in linked data)