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Re: Some comments on the spatial ontology (sdwgeo)

From: Frans Knibbe <frans.knibbe@geodan.nl>
Date: Tue, 27 Sep 2016 12:28:30 +0200
Message-ID: <CAFVDz40K-uk1agTf79CJ2BA3rw9qgCjJRShK-VU6X4YiQFi-yg@mail.gmail.com>
To: Joshua Lieberman <jlieberman@tumblingwalls.com>
Cc: SDW WG Public List <public-sdw-wg@w3.org>
Hi Josh,

Yes, I am guilty of bringing up many subjects at once. There should be a
better practice. I noticed finding a balance in how to discuss issues is a
challenge in the development of the SSN ontology too. Using GitHub to
discuss particular bits of the ontology is convenient, but lacks exposure.
I have understood that the SSN team will attempt to discuss (important)
decisions on the general e-mail list, so everything is exposed and recorded
for eternity.

Does the current spatial ontology live in a place like Github, where it is
possible for people to discuss minor details or suggest particular changes?
Also I wonder if the ontology is available online, so any examples put on
the wiki can have proper links to vocabulary terms.

Regards,
Frans



On 26 September 2016 at 15:05, Joshua Lieberman <
jlieberman@tumblingwalls.com> wrote:

> Frans,
>
> The scenario we've discussed is SDW being able to cite an OGC standard
> spatial ontology as a best practice. To process a standard, OGC needs to
> form a standards working group. It doesn't mean, however, that only OGC
> members work on the ontology or provide feedback to it. We hope that it can
> be a cooperative and publicly visible effort with everyone on the SDWWG.
>
> I agree about the interleaved email complexity,  but you did start about a
> dozen discussion threads at once here! We should pick out the most
> significant ones, I guess, and move them to the wiki.
>
> On Sep 26, 2016, at 07:28, Frans Knibbe <frans.knibbe@geodan.nl> wrote:
>
> Hello Josh,
>
> Yes, I now remember the idea of forming an OGC group to work on sdwgeo.
> How soon could that group be formed?
>
> The OGC of course is a great place to find the necessary expertise.
> However, a risk of an OGC-only group could be that the ontology will turn
> out to be a geospatial ontology, not a spatial ontology, and that it does
> not meet the requirements of general web developers, for example. I liked
> the idea of the development of the spatial ontology taking place in the
> SDWWG for that reason. Also it would probably be beneficial to have
> exposure to web communities from the start.
>
> I understand you giving up on WebProtégé. It was very hard for me to
> understand the ontology by just using WebProtégé. It is probably better to
> develop the ontology as a shared raw file that people can load into their
> editor or viewer of choice. So the  WebProtégé ontology is no longer the
> current version? I followed the link to the ontology in development on
> the wiki
> <https://www.w3.org/2015/spatial/wiki/Further_development_of_GeoSPARQL#Ontology_in_development>.
> Can we replace that link?
>
> Further replies are inline below. But it seems this way of addressing
> multiple issues in the same e-mail message gets messy very quickly.
>
> On 23 September 2016 at 21:41, Joshua Lieberman <
> jlieberman@tumblingwalls.com> wrote:
>
>> Hi Frans,
>>
>> We’ve agreed, I think, to get a group at OGC working on sdwgeo as soon as
>> possible, so visibility is good and will be improving. I’ve given up on
>> WebProtege as there is really no way to version ontologies within it even
>> when one bothers to reach a particular project.
>>
>> Responses below:
>>
>> On Sep 23, 2016, at 10:13 AM, Frans Knibbe <frans.knibbe@geodan.nl>
>> wrote:
>>
>> Hello Josh,
>>
>> Many times during the F2F meeting in Lisbon the idea that work on an
>> agreed spatial ontology is very important was confirmed for me. So I had a
>> look at the ontology in WebProtégé
>> <http://webprotege.stanford.edu/#Edit:projectId=fa09f9df-1078-4c17-a16c-ae83695ff431>
>> in its current state. You wrote that comments are welcome. I thought a
>> message like this would be the best way to share such comments,
>> although WebProtégé has its own comment system - it could be that comments
>> in WebProtégé go unnoticed and besides that all decision making should be
>> publicly recorded for eternity.
>>
>> So below are some comments and questions. Please excuse me for any stupid
>> comments, I am not an ontologist and there are probably a lot of things I
>> misunderstand.
>>
>> And I hope that more people can find the time to look at this crucial
>> piece of work.
>>
>>    1. Most importantly: Thank you for setting up the ontology!
>>    2. Earlier I asked about starting with the GeoSPARQL ontology and
>>    work from there. You answered that is not practical because WebProtégé does
>>    not seem to support refactoring. Still, it seems to me that the base
>>    classes and properties defined in GeoSPARQL 1.0.1 (gspql:geometry,
>>    gspql:SpatialObject and gspql:Feature) should be in the new ontology
>>    somewhere, if only for ensuring backward compatibility.
>>
>> The two basic entities are in there: Feature and Geometry. I removed
>> SpatialThing as the superclass of both in order to enforce the distinction
>> between recognizing a spatial thing and modeling it. So, SpatialThing is
>> set equivalent to Feature and Geometry is one possible form of
>> SpatialModel. I then moved many of the GeoSPARQL classes and entities into
>> new positions in sdwgeo following this structure.
>>
>
> Yes, that would be an improvement. But I notice gspql:SpatialObject is now
> absent from the ontology. Wouldn't that cause a backward compatibility
> issue? Or can it be assumed that gspql:SpatialObject is used nowhere?
>
>
> I doubt that anyone used it explicitly.
>
>
>>    1. I wondered if topology should be included in the ontology (see my
>>    earlier message to the list
>>    <https://lists.w3.org/Archives/Public/public-sdw-wg/2016Sep/0190.html>),
>>    but I noticed it's already in there (in the TopoModel class). I am happy to
>>    see that.
>>
>> There is a somewhat different approach between this and ISO19109 / OGC AS
>> 5. While SpatialThing and Geometry are disjoint, a SpatialThing can also be
>> a topological element. All an element does is allow topological
>> relationships and it’s much more intuitive to define those relationships
>> between the actual SpatialThing entities.
>>
>>
>>    1. SpatialThing is an important class, but its definition is not
>>    clear. It refers to ISO 19109, but that definition is not something
>>    everyone can look up. How about definitions like "Something that has some
>>    kind of spatial presence", or the current definition in the BP document,
>>    taken from the Basic Geo vocabulary: "Anything with spatial extent, i.e.
>>    size, shape, or position. e.g. people, places, bowling balls, as well as
>>    abstract regions like cubes.”
>>
>> The business model of charging for ISO specs unfortunate, to put it
>> mildly. However, ISO 19109 is equivalent to OGC Abstract Topic 5 (
>> http://portal.opengeospatial.org/files/?artifact_id=29536) which is
>> freely available. So now you can read all about the General Feature Model.
>>
>>
>>    1. Continuing the point above, can SpatialThing be defined as some
>>    sort of equivalent of geo:SpatialThing?
>>
>> The latter includes both entities in the real world and models for them,
>> so they are similar but not equivalent (some entities included in
>> geo:SpatialThing are not in sdwgeo:SpatialThing)
>>
>
> It seems to me that the definition of geo:SpatialThing is rather loose.
> Does it explicitly include models of spatial things, or try to discern
> between real world things or models of them? Tying a OGC based ontology
> like GeoSPARQL to common web ontologies seems like a very important step
> towards a truly domain-independent information model, so really trying to
> find or create common ground seems like a worthwhile effort.
>
>
> The definition of SpatialThing in W3C geo was quite loose. In sdwgeo, the
> definition is tightened up to align with the general feature model and
> exclude spatial models, which are really mathematical things.
>
>
> [snip]
>
>>
>>    1. In Lisbon we had some discussion about the computability of
>>    spatial relationships, specifically topological relationships. In my view,
>>    both SpatialThings and Geometries can have spatial relationships. In the
>>    first case, they can be used as assertions, in the second case they are
>>    computable. I
>>
>> Agreed
>>
>>
>>    1. f this view makes sense, is it useful to define two sets of
>>    spatialRelations, one for spatial things and one for geometries?
>>
>> I don’t know that we need to do that. We want to be able infer
>> relationships between features from relationships between geometries and
>> even mixtures of features and geometries.
>>
>
> But we also want to be able to make statements about spatial relationships
> between things even if no geometry is available, don't we?
>
>
> Yes, although some relationships can only be computed from geometries.
>
>
>
>>
>>    1. Another suggestion made in Lisbon: could we regard the
>>    spatialRelation 'equals' as meeting the requirement to express
>>    subject equality
>>    <http://w3c.github.io/sdw/UseCases/SDWUseCasesAndRequirements.html#SubjectEquality>
>>    ?.
>>
>> The spatial relation just says that each geometry is made up of the same
>> set of points. Not sure that spatial equality should be the same as subject
>> equality.
>>
>
> This suggestion was based on te premise that there are two kinds of
> spatial relationships: one set for spatial things (not computable) and one
> set for geometries (computable). The idea was that the 'equals' property of
> the former set could play that role.
>
> [snip]
>
>>
>>    1. Is there an entity in the ontology that can be used for expressing
>>    the array of coordinates that can be used to define a geometry?
>>
>> No, it is only a dependent property, for the reason that it is
>> meaningless without definition of the geometry.
>>
>
> I am not sure what that means exactly, one reason why I'd love to see some
> examples of how the ontology could be used. Does it mean one always has to
> use the WKT, GML or JSON literals to express the coordinates?
>
>>
>>
>>    1. I find it quite hard to see how the parts of the ontology are
>>    related. I think understanding the use of the ontology would be helped a
>>    lot with some examples (resource descriptions in RDF). I would like to try
>>    to make some examples, but what would be a good place for that? A new wiki
>>    page? Or is it better to start with a proper HTML document in GitHub that
>>    explains how to use the ontology, something that can be turned into a more
>>    or less official document?
>>
>> Examples would be good, and would presumably be moved into part of an OGC
>> spec document. Wiki for now?
>>
>
> It would make an easy start. I would not mind trying to make a new wiki
> page with some examples once I am sure of the location of the current
> ontology.
>
>>
>>
>>    1. Can other people edit the ontology? Perhaps others can contribute
>>    resource descriptions (labels and comments in different languages).
>>
>> It needs some modularization anyway. Could see about working with it on
>> GitHub to support shared work and versioning. I’ll experiment…may have to
>> go in gh-pages so that each module can be imported to another.
>>
>
> In this respect it is interesting to witness the discussion on
> modularization in SSN. It seems there might be less benefits of
> modularization there than initially thought. But if there are clear borders
> in the spatial ontology, perhaps it would help collaboration on the
> ontology, with different groups of people being responsible for different
> modules. Simplicity for end users is mostly helped by good documentation
> and good examples, I think.
>
>
>>
>>    1. Why is LinearReference a separate class? Isn't it the same as a 2D
>>    CRS?
>>
>> A linear reference system is different from a CRS. A CRS has global
>> reference geometries, while a linear reference involves identifying
>> specific linear and point features (in their own CRS’s) as the reference
>> for a linear measure. Covered exhaustively and obscurely in ISO 19148. It
>> will need separate explanation, for sure.
>>
>
> Does a CRS have to be global? I hope it will be possible to define a CRS
> in another solar system, in a building, on a piece of paper, on a  web page
> canvas or on a microscope slide, for example.
>
> If all constructs in the ontology are intended to be spatial instead of
> geospatial, does linear referencing still require its own set of constructs?
>
>
> [snip]
>
>>
>>    1. Can the ontology be related to the Location Core Vocabulary
>>    <https://www.w3.org/ns/locn>? That would give the opportunity to
>>    refer to SpatialThings by address or toponym. For example, could
>>    dcterms:Location be defined as a equivalent class or subclass of
>>    SpatialThing?
>>
>> That’s a mapping I’m still thinking about.
>>
>
> I hope it will be possible. Those kinds of links will make the ontology
> very powerful/useful.
>
> [snip]
>
> Greetings,
> Frans
>
>
Received on Tuesday, 27 September 2016 10:29:02 UTC

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