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Re: SpatialThing and feature (again)

From: Jeremy Tandy <jeremy.tandy@gmail.com>
Date: Tue, 02 May 2017 21:01:09 +0000
Message-ID: <CADtUq_0PULH0Lx1R3em+9U3porH8NFgCbLp5D2m1QFs=DO4E-Q@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>
Hi - I've added a green note the BP doc (at end of §5) via PR 781 [1]. See
the commit [2] if you want to know the details :-)

Jeremy

[1]: https://github.com/w3c/sdw/pull/781
[2]:
https://github.com/w3c/sdw/commit/89241e63b7eab37bce1f62e608dc78b2d63b3961

On Tue, 2 May 2017 at 17:20 Jeremy Tandy <jeremy.tandy@gmail.com> wrote:

> 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 21:01:55 UTC

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