[GeoSciML] URN or URL encoding of srsName EPSG codes in GeoSciML [SEC=UNCLASSIFIED]

Oliver.Raymond at ga.gov.au Oliver.Raymond at ga.gov.au
Thu Jun 25 20:47:44 EDT 2015


Hi Marcus et al,



I agree that URN vs URL for srsName is not strictly a concern of the GeoSciML standard, but I am trying to get some consistency in best practice across all our example GeoSciML instance documents because GeoSciML depends on WFS2/GML3.2.  I just had to hunt harder today to find the appropriate documentation to guide us…



1.       The OGC change request for using URL’s to identify a CRS in WFS v2 is here<https://portal.opengeospatial.org/files/?artifact_id=46445> (approved 8 July 2014). That CR notes that OGC policy is to allow URN’s, but to recommend  URL’s.  No change to WFS v2 schemas is required for this change.

2.       But, the examples in the WFS v2.0.2 schema repository (http://schemas.opengis.net/wfs/wfs-2_0_2.zip) still use URN's.  It would appear that they need updating to reflect OGC recommended policy.

3.       Geoserver - the current version (v2.7 - http://docs.geoserver.org/stable/en/user/webadmin/services/WFS.html) supports all manner of URL and URN formats for srsName.  It notes that:

a.       URN’s are the default GML v3.2 format, but they are only for WFS v1.1.1/GML v3.2 services (ie, not GeoSciML v3 or v4)

b.      The URL format http://www.opengis.net/gml/srs/epsg.xml#4326 is the default for GML v2 services (ie, not GeoSciML v3 or v4)

c.       Geoserver currently supports the URL format http://www.opengis.net/def/crs/EPSG/0/4326 that is the revised recommended WFS2/GML3.2 format.



Given all of the above, I suggest that the URL format “http://www.opengis.net/def/crs/EPSG/0/4326” should be best practice encoding for srsName in our example GeoSciML v4 documents.



Cheers,
Ollie
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Ollie Raymond
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-----Original Message-----
From: GeoSciML [mailto:geosciml-bounces at lists.opengeospatial.org] On Behalf Of Sen, Marcus A.
Sent: Thursday, 25 June 2015 6:55 PM
To: Public: A mailing list for GeoSciML
Cc: Bodor Lazar
Subject: Re: [GeoSciML] URN or URL encoding of srsName EPSG codes in GeoSciML [SEC=UNCLASSIFIED]



> -----Original Message-----

> From: GeoSciML [mailto:geosciml-

> bounces+mase=bgs.ac.uk at lists.opengeospatial.org<mailto:bounces+mase=bgs.ac.uk at lists.opengeospatial.org>] On Behalf Of

> Oliver.Raymond at ga.gov.au<mailto:Oliver.Raymond at ga.gov.au>

> Sent: 25 June 2015 07:29

> To: geosciml at lists.opengeospatial.org<mailto:geosciml at lists.opengeospatial.org>

> Cc: Lazar.Bodor at ga.gov.au<mailto:Lazar.Bodor at ga.gov.au>

> Subject: Re: [GeoSciML] URN or URL encoding of srsName EPSG codes in

> GeoSciML [SEC=UNCLASSIFIED]

>

> Ah, thanks Simon.  URL’s it is!   :-)

Hmm, maybe I'm mis-remembering but I'm pretty sure that I said exactly this; that WFS2.0.0 still specified URNs (not up-to-date with current OGC general policy) but this was one of the things that had been changed with the latest revision.



I'm pretty sure that we also concluded that we would use "HTTP-URIs" (to use the PC term for URLs :-) ) for example instances during the telecon (to go along with current OGC practice). However, there is no need, and indeed it isn't the job of the GeoSciML standard to dictate anything about this issue. For example, if a piece of WFS software has been written to conform to WFS v2.0.0 and hasn't yet been updated to support WFS v2.0.2 then it might well automatically encode spatial fields using URNs.



I just did a quick look at the meeting minutes now (which I'm afraid I hadn't looked at until now) and see that they say "Need to move to using URL's for EPSG references for complete consistency."



Marcus Sen

British Geological Survey

Keyworth

Nottingham

NG12 5GG



Web: http://www.bgs.ac.uk

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