Re: Does 'Feature' = 'Real World Thing'?

Thanks Jeremy and Linda - this begs the question: what is the relationship
between a Feature and a real world Thing, and when should we be assigning
attributes to a Feature and when to a Thing?

In some cases I expect the distinction will be important, but in others
less so.  We should try to make sure we can be flexible and not go down a
geographical version of the information resource vs non-information
resource rabbit hole.

Most common applications will want to ask questions about real world Things
and we may often be able to assign attributes directly to them (location
etc) rather than to a Feature associated with the Thing.

In other cases the distinction might be important, as I suppose a Feature
is always an approximate representation of a real world Thing, and the best
choice of how to approximate it, will depend on circumstances and purpose.



On 19 October 2015 at 08:24, Linda van den Brink <l.vandenbrink@geonovum.nl>
wrote:

> Hi all,
>
>
>
> IMO what we call features in the geospatial domain are usually
> abstractions of representations on maps of real world things; not
> abstractions of real world things themselves. I see this a lot in
> information models in the Netherlands. For example, we have two information
> models that have features of class Building. They both model exactly the
> same set of objects, but one model captures the building geometry as seen
> from above, the other from ground level. Different features, same real
> world thing...
>
>
>
> Linda
>
>
>
> *Van:* Jeremy Tandy [mailto:jeremy.tandy@gmail.com]
> *Verzonden:* maandag 19 oktober 2015 8:43
> *Aan:* SDW WG Public List
> *Onderwerp:* Does 'Feature' = 'Real World Thing'?
>
>
>
> Hi-
>
>
>
> I've been working through the discussion on Linking-Data and this
> uncovered (or, really, re-found) this issue.
>
>
>
> By OGC terminology, Feature is "an abstraction of a real world
> phenomenon". Linked Data folks like to talk about Real World Things (both
> physical and abstract).
>
>
>
> There's a disjoint here that we need to resolve.
>
>
>
> I've captured the question on the wiki [1] and included the content below.
>
>
>
> Jeremy
>
>
>
> [1]:
> https://www.w3.org/2015/spatial/wiki/Linking_Data#Question:_is_a_Feature_the_Real_World_Thing.3F
>
>
>
> Question: is a Feature the Real World Thing? ISO 19101 -- *Geographic
> information - Reference model* states:
>
> ·         [4.11] *feature*: abstraction of real world phenomena
>
> ·         [4.12] *feature attribute*: characteristic of a feature ...
>
> ·         EXAMPLE 2 A feature attribute named ‘length’ may have an
> attribute value ’82.4’ which belongs to the data type ‘real’.
>
> The definition of *feature attribute* is clear- it's a piece of
> information about the *feature*.
>
> *feature* is not quite so clear. In this context, what does *abstraction*
>  mean?
>
> Typically, the Linked Data community refer to *Real-world ‘Things’* (see Designing
> URI sets for the UK public sector
> <https://www.gov.uk/government/publications/designing-uri-sets-for-the-uk-public-sector>
> ); *real-world Things* (or just *Things*) are "are the physical and
> abstract ‘Things’ that may be referred to in statements". Examples include
> a school, a road, a person (physical); a government sector, an ethnic
> group, an event (abstract).
>
> A commonly used example is Manchester Piccadilly Railway Station. A URI
> for Manchester Piccadilly Railway Station would refer to the *real* station,
> constructed from steel and concrete with thousands of people passing
> through it each day. Clearly one cannot expect an HTTP request to return
> the real railway station (!); it returns an information object *about* the
> railway station.
>
> W3C URLS in Data (FPWD) <http://www.w3.org/TR/urls-in-data/> discusses
> the need to differentiate between the real Thing and the information
> resource that describes it. The Publishing Data
> <http://www.w3.org/TR/urls-in-data/#publishing-data> section provides
> three strategies for doing so.
>
> In the Geographic Community, the *Feature* is seen as an information
> resource - which is, in some way, related to the real-world Thing. INSPIRE (Generic
> Conceptual Model
> <http://inspire.ec.europa.eu/documents/Data_Specifications/D2.5_v3.4.pdf>)
> refers to these resources as *Spatial Objects*: "abstract representation
> of a real-world phenomenon related to a specific location or geographical
> area". It notes that the term is "synonymous with "(geographic) feature" as
> used in the ISO 19100 series" and, later, talks about versioning the
> Spatial Objects. Clearly, you can only version the record of information
> held *about* a real world Thing, not the Thing itself?
>
> So the question remains: are we identifying real-world Things (both
> physical and abstract) or information objects that describe them? Once
> that's decided, we need to get our terminology clear and stick to it!
>
>
>
>
>
>
>