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

Bill, Andrea, Josh, Simon ...

All great points; thanks!

@bill ... understanding the relationship between Thing and Feature is
crucial; this echoes the discussions we've had regarding Thing vs.
[INSPIRE] Spatial Object within the UK Location Programme. That said, let's
bottom out the definitions of both first ...

@andrea ... I think that fictional things (like Dicken's London) count as
'real-world Things'. OK; that's counter intuitive :-) ... but I'm implying
that we _talk_ about them in the real world; they are part of the "universe
of discourse".

@josh ... feature _discernment_ vs. feature _representation_; excellent &
articulate description. You raise the example of "light house" ... the same
physical thing is _discerned_ as, say, "navigation aid" for maritime and
"vertical obstruction" for aviation. Clearly, these are both valid 'views'
of the light house with respect to their domain of application. Each 'view'
of the light house will, necessarily, contain the information which is
pertinent for that application ... using your terms, there will be two
_representations_ of the lighthouse.

However, I think that your conflation of the _discerned_ feature and its
representation is problematic. Since working with RDF, I've learned that
it's very useful to be specific about the subject of each triple. For
example, attributes such as 'owner' could apply to both the light house
(physical Thing) _and_ the representation (information resource). It makes
sense to identify these separately. This is the advice from W3C URLS in
Data (FPWD) <http://www.w3.org/TR/urls-in-data/>.

Going back to the point that there are two _discerned_ features (navigation
aid & vertical obstruction) it is highly likely that the parties from the
responsible communities will mint their own identifiers for the light
house. This happens all the time ... the "non-unique-naming" problem. We
have to have mechanisms in place to allow those discerned features to be
reconciled.

That said, I think your point is that (discerned) Feature = Real World
Thing. (more or less).

@simon ... I think you're saying Feature = Real World Thing ... and Feature
Description = Information object that describes Real World Thing. Makes
sense to me. I would still say that we need to identify both the Thing and
the Information Resource - not conflate them.

Jeremy

On Tue, 20 Oct 2015 at 04:05 <Simon.Cox@csiro.au> wrote:

> I like to use ‘feature description’ to refer to the digital
> representation.
>
> Elide ‘description’ when it is obvious from context and does no other
> harm.
>
> Or use ‘description’.
>
>
>
> Ø  Different features, same real world thing...
>
>
>
> Different *descriptions*, same *feature*?
>
>
>
> Simon
>
>
>
>
>
> *From:* Linda van den Brink [mailto:l.vandenbrink@geonovum.nl]
> *Sent:* Monday, 19 October 2015 6:24 PM
> *To:* SDW WG Public List <public-sdw-wg@w3.org>
> *Subject:* RE: Does 'Feature' = 'Real World Thing'?
>
>
>
> 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
> <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!
>
>
>
>
>
>
>