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!