[postgis-devel] EMPTY

[Chris Hodgson]

I agree with you Regina, and I bet SQL Server does too.

Chris

Paragon Corporation wrote:
> They should all be false.
>
> Isn't the first requirement of containment/contains be that the two
> geometries intersect -- so if we say empty can't intersect with anything
> including empty, how can anything possibly contain  it?
>
> Though have to pull out my sql server 2008 to see if it is in agreement.
>
> Thanks,
> Regina
>
>  
>
> -----Original Message-----
> From: postgis-devel-bounces at postgis.refractions.net
> [mailto:postgis-devel-bounces at postgis.refractions.net] On Behalf Of Paul
> Ramsey
> Sent: Tuesday, October 06, 2009 4:39 PM
> To: PostGIS Development Discussion
> Subject: Re: [postgis-devel] EMPTY
>
> In the spirit of maintaining the geometry logical flow, what do you think of
> these ideas?
>
>  * ST_Contains(geometry, empty) == TRUE
>  * ST_Within(geometry, empty) == FALSE
>  * ST_Contains(empty, geometry) == FALSE
>  * ST_Within(empty, geometry) == TRUE
>
> What does SQL Server say?
>
> P
>
> On Tue, Oct 6, 2009 at 1:34 PM, Paul Ramsey <pramsey at cleverelephant.ca>
> wrote:
>   
>> I'm going to change my intersection/disjoint answers to agree w/ SQL 
>> Server. They are not bad, and they maintain the symmetry between where 
>> intersection => ! disjoint.
>>
>> P.
>>
>> On Tue, Oct 6, 2009 at 12:45 PM, Chris Hodgson <chodgson at refractions.net>
>>     
> wrote:
>   
>>> I moved these and summarized the interesting results from SQL Server 
>>> 2008 next to your original lines Paul.
>>>
>>> Note that SQL Server says that everything is disjoint from empty, 
>>> including empty itself - whereas your original guesses were to return
>>>       
> false.
>   
>>> So far I think I like SQL Server's answers. Would be good to compare 
>>> with oracle spatial too.
>>>
>>> Chris
>>>
>>> Paul Ramsey wrote:
>>>       
>>>> Regina, could you move your SQL Server examples down to a big block 
>>>> at the end, so the main part of the document is more readable? So 
>>>> far I agree with SQL Server in all the examples! Those guys are 
>>>> smart! :)
>>>>
>>>> P
>>>>
>>>> On Tue, Oct 6, 2009 at 12:12 PM, Paul Ramsey 
>>>> <pramsey at cleverelephant.ca>
>>>> wrote:
>>>>
>>>>         
>>>>> On Tue, Oct 6, 2009 at 12:03 PM, Chris Hodgson 
>>>>> <chodgson at refractions.net>
>>>>> wrote:
>>>>>
>>>>>
>>>>>           
>>>>>> I would dare say that geometry empty is more like zero, than null.
>>>>>>
>>>>>>             
>>>>> Bingo, there's a useful mental model. Wikify that!
>>>>>
>>>>>
>>>>>           
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>>>>         
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