Re: Request for comments on GeoJSON-LD vocab and context

Hi Sean, some minor points:

The context is missing a comma at the end of line 18, and has an extra comma at the end of line 19. It should be the following:

    "coordinates": {
      "@container": "@list”,
      "@id": "geojson:coordinates"
    }

Otherwise, it looks fine.

Using that context, instead of the example you show, gives somewhat different output, as coordinates are in list form, which at least allows you to preserve the order of the coordinates.

Note that there is an open feature request specifically designed for supporting the GeoJSON coordinate system [1]. Basically, this would allow you to define value mappings for an array within a context definition:

{
  "@context": {
     "coordinates": {
        "@id": "geojson:coordinates",
        "@container" : "@list",
        "@values" : { 
           "@type" : "geojson:Coordinate",
           "@container" : "@set",
           "@values" : [
               {"@type" : "xsd:double", "@id":"geo:longitude"},
               {"@type" : "xsd:double", "@id":"geo:latitude"}
           ]
        }
     }
  },
  "@graph" : [{
   "@id" : "ex:LineString1",
    "coordinates" : [
          [
            3.1057405471801753,
            51.064216229943476
          ],
          [
            3.1056976318359375,
            51.063434090307574
          ]
    ]
  }]
}
The idea is that each element of the array would be assigned a particular @type (datatype, or @id) and @id (property URI). In this case, the rendered RDF might look something like the following:

@prefix geojson: <...> .
@prefix ex: <http://example/> .
@prefix xsd: <...> .
ex:LineString1 geojson:coordinates ([
  a geojson:Coordinate ;
  geo:longitude “3.1057405471801753”^^xsd:double ;
  geo:latitude “51.064216229943476”^^xsd:double ;
], [
  a geojson:Coordinate ;
  geo:longitude “3.1056976318359375”^^xsd:double ;
  geo:latitude “51.063434090307574”^^xsd:double ;
]) .

Another proposal would introduce a JSON datatype to hold JSON values in an RDF LItera [2]l:

This might look something like the following:

    {
      "@context": {
         "coordinates": {
            "@id": "geojson:coordinates",
            "@container" : "@list",
            "@type": "@json"
         }
      },
      "@graph" : [{
       "@id" : "ex:LineString1",
        "coordinates" : [
              [
                3.1057405471801753,
                51.064216229943476
              ],
              [
                3.1056976318359375,
                51.063434090307574
              ]
        ]
      }]
    }

That could render something like the following:

@prefix geojson: <...> .
@prefix ex: <http://example/> .
@prefix xsd: <...> .
ex:LineString1 geojson:coordinates (
  “[3.1057405471801753,51.064216229943476]”^^jsonld:JSON,
  “[3.1056976318359375,51.063434090307574]”^^jsonld:JSON
) .

The former gives better RDF results, but the later is probably more generically useful.

Feedback from the GeoJSON community would be really useful in helping to set priorities for JSON-LD 1.1.

Gregg Kellogg
gregg@greggkellogg.net

[1] https://github.com/json-ld/json-ld.org/issues/397
[2] https://github.com/json-ld/json-ld.org/issues/333

> On Jan 2, 2017, at 4:27 AM, Sean Gillies <sean.gillies@gmail.com> wrote:
> 
> Dear all,
> 
> I've published an RDF vocab, JSON-LD context, HTML documentation, and PURLs for GeoJSON elements to assist those that want to process GeoJSON data in a JSON-LD context. I'd be grateful if anyone can point out unacknowledged gaps or suggest improvements in the RDF, context, or text.
> 
> http://geojson.org/geojson-ld/ <http://geojson.org/geojson-ld/>
> 
> Thanks in advance, and best wishes for the new year!
> 
> -- 
> Sean Gillies