Re: Sub-properties for locn:geometry? (was: RE: ISA Core Location Vocabulary)

On 2014-01-14 11:19, Sven Schade wrote:
>
> Geometries are points, lines, polygons, etc. For me, this should be 
> separated from the role they play in representing spatial aspects 
> (centroid, MBR, Footprint, etc.) of a ‘real world’ object.
>
> Taking an example from the source of the core location vocabulary [1], 
> a “Person” might be related to a “Location” by the properties 
> “countyOfBirth”, “countyOfDeath”, etc. A “Location” might then refer - 
> via the “geometry” property - to a “Geometry” class, which might be a 
> point, line, polygon, etc. The “Geometry” can have different relations 
> to the “Location”, e.g. a point might represent the centroid of a 
> country, a polygon might approximate the boundary.
>
> For this reason, we should look for sub-properties of “locn:geometry” 
> (as initially proposed by John), but not for sub-classes of 
> “locn:Geometry”.
>

And what about the alternative of defining them as properties of a 
geographical feature (or spatial object or spatial thing or whatever)? 
That concept has not (yet) been defined in the LOCN vocabulary, but it 
is present in other models for geographical data. We could consider 
introducing it in the vocabulary. Interestingly enough, the concept /is 
/mentioned in the definition of locn:geographicName:///"A geographic 
name is a proper noun applied to a spatial object"/.

> Best regards,
>
> Sven
>
> [1] https://joinup.ec.europa.eu/site/core_location/rdfs.html
>
> *From:*Frans Knibbe | Geodan [mailto:frans.knibbe@geodan.nl]
> *Sent:* Friday, January 10, 2014 2:24 PM
> *To:* public-locadd@w3.org
> *Subject:* Re: Sub-properties for locn:geometry? (was: RE: ISA Core 
> Location Vocabulary)
>
> On 2014-01-10 13:00, John Goodwin wrote:
>
>     Frans Knibbe wrote:
>
>     As all the subproperties are geometries themselves, why not define
>     them as subclasses?
>
>
>     The simple feature ontology does subclass geometry to polygons,
>     points etc. Are you suggesting having new classes for things like
>     ‘centroid’ (e.g. subclass of sf:Point) etc?
>
> I don't really know... I was thinking that geometries like centroid or 
> MBR are specialized geometries. They have additional constraints, like 
> a centroid always being a point and a MBR always being a rectangle. So 
> it that sense they are much like  simple feature geometry types like 
> point or polygon or multiline. But they also have other meanings, like 
> the MBR enclosing all geometry and the centroid being a 'center of 
> mass'. So if there were RDF definitions for something like the Simple 
> Features specification I guess it would make sense to view these new 
> classes as subclasses of existing types. But in many current 
> specifications, the geometry type is encoded together with the 
> coordinates, NeoGeo being an exception. It can be confusing.
>
> Given the idea that a geographical feature like a municipality can 
> have many different geometries (for instance with different levels of 
> detail), I think the idea is to associate things like centroid or MBR 
> with the feature, not with a geometry of a feature. Will that work if 
> something like a centroid is a property of a geometry?
>
> Perhaps the LOCN vocabulary should include the notion of a 
> geographical feature (something that can be modelled to have 
> geometry), so specialised geometries like MBR can be defined as 
> properties of that class?
>
> Regards,
> Frans
>
>


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