Re: Request for help: BP 9 "How to describe relative positions"

@phila - the editor of POWDER-DR must be weeping ...

On Wed, 31 Aug 2016 at 15:35 Phil Archer <phila@w3.org> wrote:

> Just on the IANA registry point, all that's needed is a list of those
> relationships. This might be in their own section or an appendix,
> something so that each term can be referenced and provide a definition.
> That may be copied from elsewhere (if credited of course). HTML5 defines
> a bunch of them [1] but you can also do it as seen at the very bottom of
> https://www.w3.org/TR/powder-dr/#appD - a spec so cruelly overlooked by
> so many people except for that one definition.
>
> Then we write to IANA (actually Mark Nottingham) and ask that they're
> added. As long as the doc is stable, he'll be happy. So I'd say that
> once we go down this road, we need to be sure that we only want to add
> new relationships as the doc evolves, not remove them. Thus they can use
> the short URL (https://www.w3.org/TR/sdw-bp/#foo).
>
> HTH
>
> Phil.
>
> [1] https://www.w3.org/TR/html5/links.html#linkTypes
>
> On 31/08/2016 10:25, Jeremy Tandy wrote:
> > Hi-
> >
> > BP doc section § 10.5.1 "Describing location" [1] is where we intend to
> > provide all the guidance that explains how you should encode location
> > information in a web-friendly way.
> >
> > This includes BP 8 "Provide geometries on the Web in a usable way" [2]
> and
> > BP 9 "How to describe relative positions" [3].
> >
> > (I think it's likely that we will also need a BP to help people choose
> the
> > right CRS too ...)
> >
> > We editors envisage BP 9 covering:
> >
> > (1) Linear referencing
> > (2) Use of spatial relations [4]
> >
> > ...
> >
> > (1)
> >>From a quick scan, I see that ISO 19148:2012 covers the topic of Linear
> > Referencing. I don't have access to the ISO document itself, so I've not
> > been able to read the standard ... but reviewing the UML model
> (accessible
> > here [5]) it seems VERY complicated.
> >
> > I also note that the INSPIRE Generic Network Model has a simpler
> > implementation of Linear Referencing.
> >
> > Questions:
> > a) are we limited to GML implementations for Linear Referencing?
> > b) has anyone converted the GML Application Schemas from ISO 19148 and
> > INSPIRE GNM into other formats ... particularly an RDF / OWL ontology?
> > c) are there any other mechanisms in use for Linear Referencing? e.g. can
> > LR be done with GeoJSON?
> > d) are people really using ISO 19148:2012 given it's complexity?
> >
> > INSPIRE's Transport Network specification v3.2 §10.3 "Linear Referencing"
> > states:
> >
> > “In general it is expected that linear referencing will be used to model
> > the relationships of objects that are associated with an network, but
> where
> > the position of those associated objects is not known (or required) to a
> > very high level of absolute accuracy ~ better than 1-3m at local level
> > (e.g. traffic accidents, planned works, restrictions).
> >
> > Where absolute accuracy is required (e.g. the location of drain covers,
> > excavations, line side signalling equipment, masts etc) such objects
> should
> > be reused, and referenced, if they already exist e.g. as topographic
> > features.”
> >
> > This seems like the basis of some guidance about when one might use
> Linear
> > Referencing.
> >
> > What I need (please!) are some worked examples for Linear Referencing of
> a
> > point along a linear feature and for Linear Referencing of a length
> along a
> > linear feature. In the flooding scenario, this might be:
> > * Location of flotsam / debris (point) blocking a drainage channel that
> > needs to manually cleared
> > * Location of a flooded section (length) of a road
> >
> > (2)
> > We also want to demonstrate how spatial relations are used. There are
> > obvious examples of topological relationships such as "this
> administrative
> > unit _touches_ that administrative unit" (or contains etc.).
> >
> > I recall that we were going to get the set of topological relationships
> > added to the IANA Link Relations registry [7]. I am not even sure which
> set
> > of topological relations we should be recommending? GeoSPARQL has me
> > somewhat confused with "Simple Features Relation", "Egenhofer Relation"
> and
> > "RCC8 Relation". Then there's D9-EIM too ...
> >
> > Can someone provide me some worked examples using the preferred set of
> > topological relationships?
> >
> > We also need to illustrate use of _directional_ (e.g. "left", "in front
> of"
> > and "astern") and _distance_ relations (e.g. "at", "nearby" and "far
> > away"). I don't know of any formalised vocabulary for expressing these
> > things. If there is one, should we be seeking to add these to the IANA
> Link
> > Relations registry too?
> >
> > Again, worked examples requested! If you can related them to an urban
> > environment / flooding scenario all the better. (e.g. someone might
> assert
> > "the flooding is near my house")
> >
> > Finally, we also need to show people how to express "fuzzy" spatial
> things.
> > Examples we have elsewhere in the BP doc are "the American West" and "
> > Renaissance Italy". These are spatial things were there is not general
> > agreement about the exact geographic extent, so it is not possible to
> use a
> > geometry to describe it. What is the best way to describe things like
> this?
> > Should we use spatial relations e.g. "downtown" _contains_ city districts
> > A, C, D, and G (because "everyone" agrees this) - but we're not saying
> it's
> > exact geometry because it's a colloquial term used by citizens of our
> > fictional Nieuwhaven.
> >
> > Again, I'd like to see a worked example.
> >
> > ...
> >
> > There's a lot of questions wrapped up in this email. I'm looking for help
> > to resolve them ... preferably with someone in the WG taking the lead to
> > coordinate a response.
> >
> > I'm also aware that we need to avoid an RDF bias, so it would be good to
> > have examples in other formats too.
> >
> > Volunteers, please step forward!
> >
> > Thanks in advance. Jeremy
> >
> > [1]: http://w3c.github.io/sdw/bp/#bp-expr-geo
> > [2]: http://w3c.github.io/sdw/bp/#describe-geometry
> > [3]: http://w3c.github.io/sdw/bp/#relative-position
> > [4]: http://w3c.github.io/sdw/bp/#spatial-relations
> > [5]: https://github.com/ISO-TC211/HMMG
> > [6]:
> >
> http://inspire.ec.europa.eu/documents/Data_Specifications/INSPIRE_DataSpecification_TN_v3.2.pdf
> >
> > [7]: http://www.iana.org/assignments/link-relations/link-relations.xhtml
> >
>
> --
>
>
> Phil Archer
> W3C Data Activity Lead
> http://www.w3.org/2013/data/
>
> http://philarcher.org
> +44 (0)7887 767755
> @philarcher1
>