Changes between Version 2 and Version 3 of DevWikiEmptyGeometry


Ignore:
Timestamp:
10/06/09 10:05:48 (15 years ago)
Author:
chodgson
Comment:

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  • DevWikiEmptyGeometry

    v2 v3  
    1515 * ST_IsSimple(empty) == TRUE
    1616 * ST_IsValid(empty) == TRUE
     17
     18''Note:''
     19It might make sense to try to maintain the geometric truisms when specifying the semantics around ''empty'' - ie. things like:
     20
     21* intersects( A, B ) => !disjoint( A, B )
     22* A == B => intersects( A, B )
     23* contains( A, B ) && contains( B, A ) => A == B
     24
     25If we don't maintain these we will probably need to complicate logical comparisons with special cases for ''empty'' - it may be the case that this is necessary, but it would be nice if it just 'came out in the wash'.
     26
     27This suggests to me that perhaps:
     28
     29* ST_Intersects( empty, empty ) == TRUE
     30* ST_Disjoint( empty, empty ) == FALSE
     31* ST_Distance( empty, empty) == 0
     32* ST_DWithin( empty, empty, tolerance) == true