Dan, The coincident first and last positions in a polygon coordinate list are in GeoRSS because they are specified that way in both OGC and ISO standards and therefore implemented that way in most every piece of geospatial software. It is hard to track down all of the reasons for this, but technically the polygon boundary is defined by linear interpolation between adjacent coordinate tuples, so it helps with consistency. The order of the coordinate positions usually has topological significance as well. Pretty much every polygon coordinate string in the world is constructed this way (including the example in (http://dev.iptc.org/rNews-10-The-Geo-Coordinates-Class , mangled a bit), so it's an interoperability issue as far as reusing geodata.
There are OWL / RDF representations defined for GeoRSS (http://www.w3.org/2005/Incubator/geo/XGR-geo-20071023/W3C_XGR_Geo_files/geo_2007.owl) and WKT or well-known-text (http://schemas.opengis.net/geosparql/) which might also be useful for defining geo-schemas. Cheers, Josh On Jun 22, 2012, at 10:57 AM, Dan Brickley wrote: > Hi folks > > Can I ask for some help with http://schema.org/GeoShape ? > > I'm working on http://schema.org/, and it's come to my attention that > we have some half-baked geo stuff in there which I'd like to get > fixed. See #geo logs below. Basically there are a bunch of structures > derived from fairly similar stuff from IPTC's rNews 1.0, which itself > seems based on GeoRSS. I'd like to fix up our docs to have plausible > examples, as well link appropriately to GeoRSS and other related > specs. > > There are more details in > http://lists.w3.org/Archives/Public/public-vocabs/2012Jun/0116.html > > Thanks for any advice, > > Dan > > 14:36 danbri: ahem, > http://stackoverflow.com/questions/10297279/what-are-the-appropriate-formats-for-the-properties-of-http-schema-org-geoshap/10466686 > 14:36 danbri: seems like we've some geo- cleanup to do in > http://schema.org/GeoShape ... advice welcomed > 14:36 danbri: details > http://lists.w3.org/Archives/Public/public-vocabs/2012Jun/0116.html > 14:46 danbri: apparently schema.org geo is based on rNews is based on geoRss > 14:47 danbri: and I'm told ... > 14:47 danbri: 'In the GeoRSS spec, you'll see that the first and last > actually are the same, 45.256 -110.45, <georss:polygon> 45.256 > -110.45 46.46 -109.48 43.84 -109.86 45.256 -110.45 ' > 14:47 danbri: in the rNews examples we don't have the repetition; I > took it to be implicit and redundant. Thoughts? > 14:49 danbri looks at http://www.georss.org/simple#Polygon > 14:50 danbri: "A polygon contains a space separated list of > latitude-longitude pairs, with each pair separated by whitespace. > There must be at least four pairs, with the last being identical to > the first (so a polygon has a minimum of three actual points)." > 14:50 danbri: is the final one acting like a check? > > _______________________________________________ > Geowanking mailing list > Geowanking@geowanking.org > http://geowanking.org/mailman/listinfo/geowanking_geowanking.org _______________________________________________ Geowanking mailing list Geowanking@geowanking.org http://geowanking.org/mailman/listinfo/geowanking_geowanking.org
