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

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”.

 

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