[postgis-devel] WKT and Wikipedia

[Martin Davis]

Agreed.

Although this is still going to break a lot of code that expects the old 
style WKT.  Perhaps it would be possible to provide a function which 
produces the old style for a few releases?

Paul Ramsey wrote:
> Be liberal in what you accept and strict in what you emit.  The
> question is, whose rules should we adhere to?  I guess, really the new
> rules are the only super-official ones, since the old SFSQL never
> actually went beyond 2D.
>
> P.
>
> On Mon, Jun 30, 2008 at 3:25 PM, Kevin Neufeld <kneufeld at refractions.net> wrote:
>   
>> That is a good question.  Since it looks like we going to break people code
>> anyway ... to be true to the spec, I assume this also means that the parser
>> should error out if someone tried to supply 3 or 4 dimensions without using
>> the POINT Z, POINT M, or POINT ZM syntax.
>>
>> We could try to be backwards compatible and continue to allow the use of
>> 'POINT' for 3D/4D coordinates, but as Martin pointed out, we would no longer
>> be compliant with the standard since the OGC standard itself is not
>> backwards compatible.
>>
>> Choose your poison, eh?
>>
>> -- Kevin
>>
>> Paul Ramsey wrote:
>>     
>>> Yes, handling POINT M, POINT Z, and POINT ZM is a good thing for 1.4.
>>> That's an addition to the parser (I can put my new lex/yacc book to
>>> use :). The hard question is what to *emit* in response to an
>>> ST_AsText() :)
>>>
>>> P.
>>>
>>> PS - those are the ISO wkt forms too.
>>>
>>> On Fri, Jun 27, 2008 at 4:42 PM, Kevin Neufeld <kneufeld at refractions.net>
>>> wrote:
>>>       
>>>> So, the 1.2 OGC specs require that the WKT of Z, M, and ZM be:
>>>> POINT <point text>
>>>> POINT Z <point z text>
>>>> POINT M <point m text>
>>>> POINT ZM <point zm text>
>>>>
>>>> PostGIS has:
>>>> POINT <point text> | <point z text>
>>>> POINTM <point m text> | <point zm text>
>>>>
>>>> To me, this means PostGIS is not entirely OGC compliant. (ie. PostGIS
>>>> can't
>>>> parse an OGC compliant WKT string)
>>>>
>>>> postgis=# SELECT 'POINT ZM(0 0 0 0)'::geometry;
>>>> ERROR:  parse error - invalid geometry
>>>>
>>>> Same goes for the textual representation of other geometries.
>>>> ie. LINESTRING ZM (...)
>>>>
>>>> Should we add this to the TODO list for 1.4?  Or is there a specs gray
>>>> area
>>>> ... that we're compliant enough.
>>>>
>>>> -- Kevin
>>>>
>>>> Martin Davis wrote:
>>>>         
>>>>> Actually the latest SFS 1.2 spec does include a spec for 2D measured, 3D
>>>>> &
>>>>> 3D measured WKT.  See here:
>>>>>
>>>>> http://www.opengeospatial.org/standards/sfa
>>>>>
>>>>> (This is also referenced on the wiki page)
>>>>>
>>>>>
>>>>>
>>>>> Kevin Neufeld wrote:
>>>>>           
>>>>>> I just came across this page:
>>>>>> http://en.wikipedia.org/wiki/Well-known_text
>>>>>>
>>>>>> I think this page is incorrect, misleading, and contains typos.  It is
>>>>>> my
>>>>>> understanding that the OGC specs on WKT does *not* include 3D and 4D
>>>>>> definitions.  It is a PostGIS extension to use Z, M, or ZM. Or am I off
>>>>>> on
>>>>>> this?
>>>>>> (http://portal.opengeospatial.org/files/?artifact_id=829) (section
>>>>>> 3.2.5.2)
>>>>>>
>>>>>> I don't have an account to correct this.  Does any here have one?  Do
>>>>>> we
>>>>>> care?
>>>>>>
>>>>>> Should the new PostGIS docs reference such pages, or point to only the
>>>>>> OGC specs?
>>>>>>
>>>>>> -- Kevin
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>>>>>>
>>>>>>             
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>   

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022