RE: SpatialThing and feature (again)

Hold on a moment folk – does this problem really exist?

I’m looking at http://www.w3.org/2003/01/geo/wgs84_pos# which is the RDF/XML serialization of W3C Basic Geo.
Here’s the key axioms.

geo:lat   rdfs:domain geo:SpatialThing .
geo:long rdfs:domain geo:SpatialThing .
geo:Point rdfs:subClassOf geo:SpatialThing .

So a resource carrying the lat/long properties implies that it is a SpatialThing, not only the Point subclass.

And from http://schemas.opengis.net/geosparql/1.0/geosparql_vocab_all.rdf

since

geosparql:Geometry rdfs:subClassOf geosparql:SpatialObject .

then it looks to me like

geo:SpatialThing owl:equivalentClass geosparql:SpatialObject .
geo:Point rdfs:subClassOf geosparql:Geometry .

and there is no inconsistency. Appearance of geo:lat and geo:long properties only entails that it is a geosparql:SpatialObject, so can be either a Feature or a Geometry.

Am I missing something?

Simon

From: Rob Atkinson [mailto:rob@metalinkage.com.au]
Sent: Thursday, 20 April, 2017 06:24
To: Joshua Lieberman <jlieberman@tumblingwalls.com>; Andreas Harth <harth@kit.edu>
Cc: public-sdw-wg@w3.org
Subject: Re: SpatialThing and feature (again)


This could also be resolved by thinking of geo:long as a property that can entail a geometry property of the feature - maybe its even a geometry property in the same way that a 2D point is a partial representation of a 3D location?

Rob

On Thu, 20 Apr 2017 at 02:38 Joshua Lieberman <jlieberman@tumblingwalls.com<mailto:jlieberman@tumblingwalls.com>> wrote:
Andreas,

It may not be worth delving too deeply into this...

W3C Basic Geo defines SpatialThing and then subclasses it to Point carrying the lat and long properties. No one defines their own SpatialThings, they simply add geo:lat and geo:long properties to some resource X to turn it into “also a Point”, in other words “also a geometry”. This implies for most users but does not actually assert that resource X is both a feature and a geometry. One could form a subclass of geo:SpatialThing that was actually disjoint with geo:Point or other geometry,  which would then align more-or-less with iso geosparql:Feature, hence the assertion that some geo:SpatialThings are geosparql:Features. This is largely hypothetical.

There is a similar property in GeoRSS, the point(pos) property, but this doesn’t try to create one feature-geometry amalgam. It’s simply a shortcut for a longer expression that identifies some resource as a _Feature with a “where" object property connecting to a Point geometry resource.

It might be most accurate to say that your example of using W3C Basic Geo to represent feature and geometry in the “style” of geosparql is actually the longhand of what people are trying to do when they do use geo:lat and geo:long, identifying a resource as a real world feature and giving it a closely allied point geometry.

—Josh

> On Apr 19, 2017, at 11:54 AM, Andreas Harth <harth@kit.edu<mailto:harth@kit.edu>> wrote:
>
> Hi,
>
> On 04/19/17 13:29, Joshua Lieberman wrote:
>> My understanding based on the limited documentation is that w3cgeo:SpatialThing covers both features and models such as geometries, so
>
> that's my understanding too.  With the W3C WGS84 vocabulary you can write:
>
> @prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#<http://www.w3.org/2003/01/geo/wgs84_pos>> .
> @prefix : <#> .
>
> :bob a geo:SpatialThing ; geo:lat "52.5196143" ; geo:long "13.4065603" .
>
> So the resource with the URI :bob is both the "feature" and the "geometry".
>
> In other representations (NeoGeo, GeoSPARQL), you would identify two separate
> resources:
>
> @prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#<http://www.w3.org/2003/01/geo/wgs84_pos>> .
> @prefix : <#> .
>
> :bob a :Feature ; :geometry _:bnode .
> _:bnode a :Geometry , geo:Point ; geo:lat "52.5196143" ; geo:long "13.4065603" .
>
> The URI :bob now represents the "feature" resource, and the blank node _:bnode
> represents the "geometry" resource.
>
> I wouldn't know how to write OWL axioms to map the two modeling choices though.
>
> Best regards,
> Andreas.
>
>