-------- Original Message --------
Subject: Re: [Geoserver-devel] wfs 1.1 cite update
Date: Thu, 24 May 2012 13:54:15 +0800
From: Ben Caradoc-Davies
To: Justin Deoliveira
On 24/05/12 12:39, Justin Deoliveira wrote:
> * New srs format
> Currently for wfs 1.1 we use the original srs urn syntax as specified in
> the original version of the wfs 1.1 spec. Which looks like:
> The mandated format has been changed "mid-spec" and now the tests
> mandate that the format look like:
> Note the "double colon" between the authority and code, that is not a typo.
Correct. This element is for the version of the EPSG database. In
general, urn:ogc versions are optional (hence the double colon), but OGC
insist on their inclusion in the case of EPSG: "The “version” part shall
be included in this case, since the EPSG sometimes deprecates and
replaces existing definitions." From: "URNs of definitions in ogc
namespace" (OGC 05-010):
I don't like this as it is yet another point of variation to confuse
clients. I am more than happy to have the version left blank, but this
might cause cite compliance problems later.
> So... what to do. As I see it we have a few options.
> (1) Update this across the board and just output the new form by default.
> (2) Only use this form when cite compliance is turned on.
> (3) Add this new form as a new possibility for GMLInfo.getSrsNameStyle()
> making it configurable to use the new style, updating the wfs 1.1 cite
> configuration to use the newest version and possibly keeping the default
> configuration using the existing style
> All in all I think (3) is probably the most ideal, but represents the
> most work. (1) is the easiest. Curious to here what people think about
> this one.
(1) may break existing clients.
(2) makes we worry that some users will be stuck with all
cite-compliance options when they only want one.
I like (3), which is also extensible to support the new HTTP URI form
(e.g. http://www.opengis.net/def/crs/EPSG/0/4326). You could also add
support for an OGC URN with EPSG version (e.g.
urn:ogc:def:crs:EPSG:6.3:4326). I suspect that (3) will put us in a
position to add new formats almost as fast as OGC can invent them.
Here are two current Jira issues:
Support in WFS for HTTP URIs like:
is before the WFS/FES SWG and will likely be included in WFS 2.1. See:
"Allow use of http URIs to identify CRS" (WFS/FES change request 11-152):
"OGC Identifiers – the case for http URIs" (OGC 10-124r1):
HTTP URIs are current OGC policy:
"In June 2010 OGC revised the naming policy to use http URIs to identify
persistent OGC resources instead of URNs."
Youse might also be interested in Simon's recent seminar on controlled
vocabularies (slides and audio):
Simon explains why HTTP URIs are useful because they allow the
implementation of Tim Berners-Lee's Linked (Open) Data rules, and
describes some successful patterns for using them.
CSIRO Earth Science and Resource Engineering
Australian Resources Research Centre