Re: SpatialThing and feature (again)

Noted. I think that we should express it like this - but note the ambiguity
in definition.

I remember @danbri saying not to get too hung up of W3C Basic Geo as there
wasn't a lot of thought that went into it ...
On Fri, 21 Apr 2017 at 17:40, Joshua Lieberman <jlieberman@tumblingwalls.com>
wrote:

> Jeremy,
>
> A pretty good summary. One might interpret the W3C Basic Geo properties as
> mapping to a geometry property (as GeoRSS Simple does), but there isn’t
> conclusive evidence that this was originally intended.
>
> Josh
>
> On Apr 21, 2017, at 11:33 AM, Jeremy Tandy <jeremy.tandy@gmail.com> wrote:
>
> Hi all-
>
> I've spent more than a few minutes parsing through the email chain.
>
> 1/ Clemens' summary (from mid way though) suggests that (a) ISO 19109
> Feature is [also] a geosparql:Feature, (b) these may or may not have
> attached geometry properties
> 2/ Andrea suggests that "only [those] ISO 19109 Features [with spatial
> extent] are Spatial Things according to the BP definition" - but Josh
> suggests we're using "spatial extent" as a shorthand for "real-world
> phenomena", and that "making the connection [between abstraction and
> real-world thing] formal and explicit is not necessary for Web purposes"
>
> So I'm seeing that there's no inconsistency to explain away.
>
> Please confirm that I've read this OK. Apologies if I've missed the point!
>
> And, talking of Points ... I see that there is potential for confusion
> regarding the "Feature/Geometry amalgam".
>
> We could insert a "green note" into the BP document identifying the
> potential for inconsistency - as defined in Andreas' example:
>
> > Because a w3cgeo:SpatialThing has lat/lon, some people might equate a
> w3cgeo:SpatialThing with a geosparql:Geometry.
> >
> > Because the w3cgeo:SpatialThing is an instance of foaf:Person, some other
> people find it natural to equate the w3cgeo:SpatialThing with a
> geosparql:Feature.
> >
> > Based on data from different source we now have an inconsistency, because
> the w3cgeo:SpatialThing is an instance of both geosparql:Feature and
> geosparql:Geometry, which are defined as disjoint.
>
> ... and reaffirm that _we_ see Feature (SpatialThing) as disjoint from
> geometry, but that this might be at odds with some people's
> interpretations. As Josh says: "we can’t really say there is a mapping
> from W3C Basic Geo to/from anything based on 19109."
>
> Am I summarising correctly?
>
> Thanks, Jeremy
>
>
> On Fri, 21 Apr 2017 at 15:33 Joshua Lieberman <
> jlieberman@tumblingwalls.com> wrote:
>
>> Ah, I had thought that the domains of geo:lat and geo:lon were geo:Point,
>> since that is what is generally referred to in narrative. If a resource
>> carrying the lat/lon properties implies that it is a SpatialThing, not only
>> the Point subclass, adding the properties doesn’t resolve any feature /
>> geometry ambiguity. Your equivalences are certainly possible, but geosparql
>> doesn’t / shouldn’t support adding direct positions to features, so
>> entailing something with geo:lat and geo:lon as geosparql:SpatialObject
>> rather than geosparql:Geometry doesn’t really work. And if we can’t derive
>> that use of geo:lat and geo:lon imply both a feature and a geometry, than
>> Andrea is correct that we can’t really say there is a mapping from W3C
>> Basic Geo to/from anything based on 19109. That may be unfortunate.
>>
>> —Josh
>>
>> On Apr 20, 2017, at 8:38 PM, simon.cox@csiro.au wrote:
>>
>> 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 .
>>
>>
>>
>> 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
>> <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> 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> 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.
>> >
>> >
>>
>>
>