[postgis-users] geos result sets

[David Blasby]

Martin Davis wrote:
  > Oracle Spatial does provide a notion of tolerance in its spatial
> relationship operators.  However, I have never seen a description of the
> actual semantics of the tolerance value, so I don't feel that I fully
> understand what it does or how it could be implemented.  It would be an
> interesting exercise to try and define a tolerance-based semantics for
> spatial relationships. (If anyone is aware of such a thing please let me
> know).  If this proved useful it would of course be nice to add it to
> JTS/GEOS.

I think this is much easier for oracle since they dont do a the 
dimentionally-extended 9 matrix (ie. every cell is "T/F" not "F/0/1/2").

There for you can define things like (for geometry A and B):

(b = boundary, i = interior, e=exterior)

interact_Ab_Bb = A.getBoundary().distance( B.getBoundary() )   < tol
interact_Ab_Bi = A.getBoundary().distance( B )   < tol
interact_Ab_Ae = A.getBoundary().distance( B )  > tol  //not sure

etc...

NOTE: for the above purposes the "interior" of a polygon is the polygon, 
"interior" of a line is the line, and "interior" of a point is the point.

I think you'd have to do a bunch of oracle testing to find out - I've 
never seen a good definition of their predicates.

dave