[postgis-devel] Motion: vote for considering SRID <= 0 as "unknown"
pramsey at opengeo.org
Tue Oct 4 10:20:51 PDT 2011
For the difference between "implementation-defined" and
Basically the spec is saying that 0 is the only "special value"
allowed, and we can say what its specialness is.
On Tue, Oct 4, 2011 at 10:18 AM, Paul Ramsey <pramsey at opengeo.org> wrote:
> I love ISO language.
> On Tue, Oct 4, 2011 at 10:11 AM, Chris Hodgson <chodgson at refractions.net> wrote:
>> Sandro Santilli wrote:
>>> On Tue, Oct 04, 2011 at 03:54:28PM +0100, Mark Cave-Ayland wrote:
>>>> My only comment would be what do the various standards (SQL-MM/OGC)
>>>> say about SRID values? As long as they don't specify anything, I
>>>> guess we have a bit more freedom to interpret the specification as
>>>> fits best with PostGIS.
>>> All I can find about SRID in OGC SFS 1.1:
>>> Before a geometry can be constructed and inserted into a table,
>>> the corresponding row for its SRID must exist in the
>>> SPATIAL_REFERENCE_SYSTEMS table, else construction of the geometry
>>> will fail.
>>> There's no mention of the possibility for a geometry to have _no_ srid.
>>> The SRID field in spatial_ref_sys and geometry_columns is of type
>>> "integer" (but there's no case of "unsigned" in the whole document so
>>> that isn't necessarely a sign of the fact that we should support <0).
>>> The SQL/MM doesn't seem any different in that reguard. In both there's no
>>> concept of "unknown" srid.
>> I thought the entire motivation for switching to the unknown=0 semantic was
>> for some kind of standards compliance... if this isn't in any standard, why
>> are we doing it again? (I'm seriously asking the question - what is the
>> positive side of this change?)
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