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RE: Some comments on the spatial ontology (sdwgeo)

From: <Simon.Cox@csiro.au>
Date: Mon, 26 Sep 2016 00:08:40 +0000
To: <frans.knibbe@geodan.nl>, <jlieberman@tumblingwalls.com>
CC: <public-sdw-wg@w3.org>
Message-ID: <693abba19e4d4db3b42c853fc880e6df@exch1-mel.nexus.csiro.au>
Ø  It refers to ISO 19109, but that definition is not something everyone can look up.

As mentioned a couple of times earlier, the full glossary of definitions from ISO 19100-series standards are available at [1] and I also put up a provisional linked-data representation at [2] (will be superseded by an official one soon – I’m assisting in its preparation.)

I strongly suggest that we make use of and reference to this glossary, since it is already used by all those agencies that endorse the ISO standards. The definitions may not be exactly what you would write, but it would be a serious mistake for the SDWWG to adopt definitions that clashed with the ISO ones.

[1] http://www.isotc211.org/Terminology.htm

[2] http://registry.it.csiro.au/sandbox/iso-tc211/terms

From: Frans Knibbe [mailto:frans.knibbe@geodan.nl]
Sent: Saturday, 24 September 2016 12:13 AM
To: Joshua Lieberman <jlieberman@tumblingwalls.com>
Cc: SDW WG Public List <public-sdw-wg@w3.org>
Subject: Some comments on the spatial ontology (sdwgeo)

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.
  3.  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.
  4.  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."
  5.  Continuing the point above, can SpatialThing be defined as some sort of equivalent of geo:SpatialThing?
  6.  I assume the intention of the SpatialModel class is that it can represent a model of a SpatialThing. Shouldn't it say so in its definition/comment?
  7.  If Extent is not defined as it usually is understood (an indication of the space a spatial thing occupies), but as a synonym of dimensionality, then why is Extent a subclass of SpatialModel?
  8.  If Extent is not meant to be used to indicate the space a spatial thing occupies (e.g. a minimal bounding rectangle), then which part of the ontology is meant for that?
  9.  In a general view of spatial relations there are three types: topological relations (e.g. within, crosses), distance relations (e.g. at, near to, far from)  and directional relations (e.g. north of, upstairs from, behind). Would it make sense to define these types as subproperties of spatialRelation, and let the current set of subproperties be subproperties of e.g. topologicalRelation?
  10. 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. If this view makes sense, is it useful to define two sets of spatialRelations, one for spatial things and one for geometries?
  11. 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>?
  12. I see that the property hasSerialization has three subproperties: asGML, asJSON and asWKT. But GML, JSON and WKT have very different levels of expressiveness. For example, WKT has no way of expressing CRS or resolution. JSON, on the ohter hand, is a very general format so it is not so clear what the serialization would look like. Or did you mean GeoJSON?
  13. 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?
  14. 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?
  15. Can other people edit the ontology? Perhaps others can contribute resource descriptions (labels and comments in different languages).
  16. Why is LinearReference a separate class? Isn't it the same as a 2D CRS?
  17. I see a property 'resolution' has been defined. But it does not seem to be related to other entities. Will it be a property of SpatialModel?
  18. 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?
  19. Can the range of spatialDimension be specified as one the integers 1, 2 or 3?

This is what I've come up with now. Probably questions will disappear or form when understanding increases. Having a set of examples of how the ontology can be used would probably help a lot for that understanding, and I think that working of implementation examples from our own fields of work could be a fun & fruitful group activity.

Received on Monday, 26 September 2016 00:09:29 UTC

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