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Re: [dxwg] Spatial coverage [RSC] (#83)

From: Andrea Perego via GitHub <sysbot+gh@w3.org>
Date: Thu, 07 Mar 2019 00:08:46 +0000
To: public-dxwg-wg@w3.org
Message-ID: <issue_comment.created-470328290-1551917325-sysbot+gh@w3.org>
This issue was discussed by the DCAT subgroup on 6 Mar 2019, and I got [an action](https://www.w3.org/2019/03/06-dxwgdcat-minutes#x05) to make a proposal.

I think it is probably better to split the proposal in two, and I would first go for the issue concerning the fact that we lack specific properties for specifying bboxes and centroids. 

**Proposal 1**

So, my proposal nr. 1 is to define two corresponding properties in the DCAT namespace:
- `dcat:bbox`
- `dcat:centroid`

The range of these two properties may depend on the decision taken about proposal nr. 2 below, so for the moment I leave it undefined.

**Proposal 2**

The proposal nr. 2 is about how to specify the geometry itself. In this case, I would ask for a vote on 3 possible proposals:

- **Proposal 2.a**: re-use `locn:geometry`, following what done in GeoDCAT-AP (as explained earlier in this conversation). The range will be a geometry literal (e.g., WKT)

- **Proposal 2.b**: define a property, equivalent to `locn:geometry` in the DCAT namespace - namely, `dcat:geometry`. The range will be a geometry literal (e.g., WKT)

- **Proposal 2.c**: use GeoSPARQL

Proposals 2.a and 2.b address the issue I mentioned earlier in this discussion of reducing the "distance" in the graph between the dataset and the geometry itself. So, it gives a more flat specification of the spatial coverage compared with GeoSPARQL.

Putting this into examples (re-using @nicholascar 's ones):

- Proposal 2.a - `locn:geometry`:

a:Dataset dct:spatial a:Location .

a:Location a dct:Location ;
  locn:geometry "<http://www.opengis.net/def/crs/OGC/1.3/CRS84> Point(-0.001475 51.477811)"^^gsp:wktLiteral .

- Proposal 2.b - `dcat:geometry`:

a:Dataset dct:spatial a:Location .

a:Location a dct:Location ;
  dcat:geometry "<http://www.opengis.net/def/crs/OGC/1.3/CRS84> Point(-0.001475 51.477811)"^^gsp:wktLiteral .

- Proposal 2.c - GeoSPARQL:

a:Dataset dct:spatial a:Location .

a:Location a dct:Location ;
  gsp:hasGeometry [ 
    a sf:Point; 
    gsp:asWKT "<http://www.opengis.net/def/crs/OGC/1.3/CRS84> Point(-0.001475 51.477811)"^^gsp:wktLiteral 
] .
Looking forward to your votes & feedback.

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Received on Thursday, 7 March 2019 00:08:47 UTC

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