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Re: SpatialThing and feature (again)

From: Jeremy Tandy <jeremy.tandy@gmail.com>
Date: Tue, 02 May 2017 16:20:04 +0000
Message-ID: <CADtUq_1CYx6fTKsUScOSyOtLPjho2eTeAY3UgDxxUKb491SzUA@mail.gmail.com>
To: Clemens Portele <portele@interactive-instruments.de>
Cc: Matthew Perry <matthew.perry@oracle.com>, "public-sdw-wg@w3.org" <public-sdw-wg@w3.org>
Thanks Clemens.
On Tue, 2 May 2017 at 17:18, Clemens Portele <
portele@interactive-instruments.de> wrote:

> Hi Jeremy,
>
> I see your point and I guess you are right. I still think that the
> description is quite fuzzy and it is not obvious that "anything with
> spatial extent" is not meant to be narrower than the ISO 19109 concept of a
> feature *), which is partly why I started the thread. But the text is quite
> challenging for new readers already due to all the legacy of terms and
> definitions that are not well aligned and adding more nuanced discussion is
> probably not helpful. So I am ok with leaving it as it is. We always
> reference back to the email thread ;)
>
> Thanks,
> Clemens
>
> *) I am ignoring here for simplicity that spatial thing includes not only
> the abstraction, but also the real-world entity.
>
>
> On 2. May 2017, at 17:52, Jeremy Tandy <jeremy.tandy@gmail.com> wrote:
>
> 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 16:20:54 UTC

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