WG discussion: shall we recommend a "samePlaceAs" property?

Hi - for this sprint in development of the Best Practice document, we're
updating BPs about "linking" and "vocabularies" ...

On multiple previous occasions (most recently the London F2F) we've
mentioned that we should propose a "samePlaceAs" property. In essence, I
think we see this as a subjective statement (that a human might make)
rather than a mathematical / topological statement, matching on the spatial
characteristics only.

This addresses the concerns about the VERY restrictive owl:sameAs. At
TPAC2016, @clemens said that a "relaxed relationship is better [for
cross-referencing identifiers] (e.g. samePlaceAs) … but if you _can_ state
owl:sameAs then you should do so … " [from my notes]

We said at TPAC2015 "samePlaceAs would be a 'social relationship' - based
on people's perception".

The domain and range should both be "spatial things" (which definition of
spatial thing do we refer to - the new one coming from @josh's work or
w3cgeo:SpatialThing?

We're looking to resolve this question BEFORE the Delft F2F.

WG members: what do you think?

Many thanks, Jeremy

further notes below:

---

My notes from the most recent discussion during London F2F are here:

   - "samePlaceAs"
   - it would be an IANA link relation identifier


   - equivalence at a geographical level - without a formal definition of
      that equivalence
      - geography related
      - don't express as a sub-property of, for example, "so:matches" [
      https://files.ifi.uzh.ch/ddis/iswc_archive/iswc/pps/web/iswc2010.semanticweb.org/pdf/261.pdf]
      … we're only indicating that the _spatial_ properties match ... and
      property hierarchies just get complicated to 95% of humans
      - not a mathematical statement (like the topological relationships)
      - avoid any "mereological" confusion [ :) ]
      - nearby? (& other fuzzy relationships) ... same-place-as is _so_
      common that we'll deal with it as a special case and _not_ cover these
      other spatial relationships for now
      - which ontology? IANA Link Relations
   - ... not used today- so not a _best_ practice
   - ... assert as a [recommended] approach to resolve problems we see in
   evidence today- especially regarding incorrect use of owl:sameAs

---

And back on the BP call on 9-Nov we said:

*jtandy:* Another aspect to discuss is the reuse of identifiers ("to keep
the global graph intact").

... But to be able to add additional information and make it retrievable it
requires a new identifier with a sameAs-like link to the "known identifier"

... "samePlaceAs"?

*eparsons:* samePlaceAs sounds restrictive

*jtandy:* agrees, we want to avoid the strong nature of sameAs

*ByronCinNZ:* likes the idea, very geographic statement. In which ontology
would this reside?

*ClemensPortele:* I think we said it would be an IANA link relation
identifier

*jtandy:* As it does not exist yet, we cannot claim it is a "best practice"

*eparsons:* I think this problem will be hard to avoid, but it could be
described as a way to address the issue

*ChrisLittle:* worried about "samePlaceAs". How does it fit with the
algebra of polygons?

*jtandy:* we don't want to be too specific

... ... at TPAC we had a discussion about the well-defined topological
relationships

*eparsons:* to get something done quickly we should try to keep it simple

... ... relationships could be tackled later

*jtandy:* so we agree that samePlaceAs is not intended as a mathematical
statement

<*ClausStadler_*>
https://files.ifi.uzh.ch/ddis/iswc_archive/iswc/pps/web/iswc2010.semanticweb.org/pdf/261.pdf

<*ClausStadler_*> "so:matches Two URIs refer to possibly distinct things
that share all the prop- erties needed to substitute for each other in some
graphs. Th is property is symmetric but not necessarily reflexive.
so:matches is a super-property of so:identical ."

*ByronCinNZ:* agrees, and this is probably the most important of the
topological relationships

*ClausStadler_:* Explains the paper and "so:matches" reference (see above)

*jtandy:* yes, there is overlap. we want to focus on the spatial match.

*ClausStadler_:* could be a sub-property

*jtandy:* worried on nesting, maybe it makes it overcomplicated

I agree with the concern

<*eparsons*> +1

*eparsons:* worried about complication, too

<*AndreaPerego*> +1

*ByronCinNZ:* should be a top-level relationship