Re: [dxwg] Spatial coverage [RSC]

Sorry to jump in here so late. 

I should probably provide a bit of context for explaining the reasons behind the design choices of `locn:geometry` and its use to specifying the spatial coverage of a dataset.

So, the reason why the range of [`locn:geometry`](https://www.w3.org/ns/locn#locn:geometry) was left open is twofold:
- We had use cases requiring the specification of a geometry directly as a literal, without using specific classes. 
- We had also use cases requiring a more sophisticated geometry specifications (as in GeoSPARQL). Nonetheless, at the time when LOCN was defined, there was no widely used vocabulary/approach for doing, this (yes, GeoSPARQL was out, but not used across domains). So, we focussed on identifying the most used options. 

Coming now to the use of `locn:geometry` in GeoDCAT-AP (which is more relevant here), the issue was to find out how to represent the spatial coverage from ISO 19115 records, which, in the majority of the cases, is done with a bbox.

DCAT didn't provide any guidance on this. Moreover, the GeoDCAT-AP WG re-stated the requirement of being able to directly specify the bbox as a literal. So, the choice of `locn:geometry` was pretty straightforward, and all discussion focussed instead on which should be the recommended geometry encoding (the most voted options being GML, WKT and GeoJSON).

The use of `locn:geometry` along these lines has been also documented in the W3C/OGC Spatial Data on the Web BPs - see, e.g., [Example 15](https://www.w3.org/TR/sdw-bp/#ex-geodcat-ap-bag-addresses).

Based on the implementation experiences I'm aware of, the use of `locn:geometry` in this way has not raised any specific problem. Rather, the issue (that we had also when developing GeoDCAT-AP) is that there is no established practice on how to specify bboxes in RDF (and even centroids). However, as far as I can understand, working on this is not in scope of the DXWG.

BTW, this was also one of the issues discussed at length in the LOCADD CG ([there's a page summarising the discussion](https://www.w3.org/community/locadd/wiki/Use_case:_Sub-properties_for_locn:geometry)), and then inherited by the SDWWG, but no solution has been provided. 

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Received on Thursday, 8 March 2018 22:42:40 UTC