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Re: SpatialThing and feature (again)

From: Jeremy Tandy <jeremy.tandy@gmail.com>
Date: Tue, 02 May 2017 15:52:01 +0000
Message-ID: <CADtUq_0qrAGhfTs_VMbjrzc2P3QknWpvWPeM4rPoaKcPYzECHw@mail.gmail.com>
To: Matthew Perry <matthew.perry@oracle.com>, public-sdw-wg@w3.org
Hi - I'm just in the process of updating the BP document to reflect our
discussion.

Clemens suggested that we explicitly call out things like "home loan" as an
example of a spatial thing. Having read through the text, it feels like
this is a fairly nuanced statement that A/ may lead to more confusion,
unless B/ we take time to describe why something that appears to not have
spatial extent really does.

Personally, I'd rather leave this complexity out.

What do you think? (especially Clemens)

Jeremy

On Tue, 25 Apr 2017 at 12:58 Jeremy Tandy <jeremy.tandy@gmail.com> wrote:

> Thanks all. I can amend the BP doc to clarify as per Simon's proposal.
> Jeremy
> On Tue, 25 Apr 2017 at 12:54, Matthew Perry <matthew.perry@oracle.com>
> wrote:
>
>> That looks correct to me as well.
>>
>> Thanks,
>> Matt
>>
>> On 4/25/2017 12:29 AM, Joshua Lieberman wrote:
>>
>> Yes, I think.
>>
>> On Apr 25, 2017, at 12:19 AM, <Simon.Cox@csiro.au> <Simon.Cox@csiro.au>
>> wrote:
>>
>> Ø  ... 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."
>>
>> We need to be very clear here:
>>
>> geosparql:SpatialObject         includes both features and geometries –
>> they are disjoint subclasses
>> w3cgeo:SpatialThing               is superclass of w3cgeo:Point, but
>> (OWA) potentially also has a class of features as another subclass
>> (disjoint from Point) – so this could all be OK and consistent (but we
>> mustn’t credit w3cgeo as having been the result of much deep thought).
>>
>> So where does bp:SpatialThing fit in? Looks to me like the key thing is
>> to point out that it is **not** the same as w3cgeo:SpatialThing, because
>> the latter includes geometries. But it **is** the same as
>> geosparql:Feature, which is disjoint from Geometry.
>>
>> Simon
>>
>> *From:* Clemens Portele [mailto:portele@interactive-instruments.de
>> <portele@interactive-instruments.de>]
>> *Sent:* Tuesday, 25 April, 2017 01:27
>> *To:* Jeremy Tandy <jeremy.tandy@gmail.com>
>> *Cc:* Josh Lieberman <jlieberman@tumblingwalls.com>; Cox, Simon (L&W,
>> Clayton) <Simon.Cox@csiro.au>; Rob Atkinson <rob@metalinkage.com.au>;
>> Andreas Harth <harth@kit.edu>; public-sdw-wg@w3.org
>> *Subject:* Re: SpatialThing and feature (again)
>>
>> Hi Jeremy,
>>
>> I think we should add a green note in chapter 5 to explain how the
>> "anything with spatial extent" definition is consistent with features like
>> a "home loan" in a spatial dataset as it is not obvious.
>>
>> Clemens
>>
>>
>>
>> On 21. Apr 2017, at 17:33, 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#
>> <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.
>> >
>> >
>>
>>
>>
>>
Received on Tuesday, 2 May 2017 15:52:47 UTC

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