[postgis-devel] Call for 1.4.2 and 1.5.1 (Handling of Invalid Geometries)

[Martin Davis]

Well, so it's still invalid.  So what?  Bottom line is that someone 
handed in garbage claiming it was a LinearRing.  They can't complain 
about being told that no, it's actually garbage.

The idea is to allow more cases to enter the database in a graceful way, 
without requiring a huge effort to check for bad structure throughout 
the codebase.  There's no promise to perform magic.  There will always 
be geometries which are so badly munged that they can't be made valid no 
matter what.

strk wrote:
> On Wed, Feb 17, 2010 at 11:36:05AM -0800, Martin Davis wrote:
>
>   
>> I agree that users should be allowed to load topologically invalid data, 
>> but structurally invalid data seems like it's more trouble to handle 
>> than it's worth.  Is it not an option to simply always close rings on 
>> input to the database? 
>>     
>
> Close the ring below and you'll see how much of an option that is:
>
>  +-----------+
>  |           |
>  | +-------+ |
>  | | +---+ | |
>  | | |   | | |
>  |   |   |   |
>  +---+   +---+
>
> You'd go from structural invalidity to topological invalidity.
>
>   
>> If you allow structurally invalid rings into the database, I think you 
>> wind up with a situation where users never know if their data is OGC SFS 
>> compliant or not - which I think would do more harm than good to the 
>> repuation of PostGIS.
>>     
>
> Isn't this the whole reason for ST_isValid to exist ?
>
> --strk;
>
>   ()   Free GIS & Flash consultant/developer
>   /\   http://foo.keybit.net/~strk/services.html
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>   

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