Format of VALIDATE_GEOMETRY_WITH_CONTEXT output

Question

Hi,
I'm trying to write a generic routine to display validation errors (e.g. show the geometry with the erroneous segments highlighted), with the aim to more easily correct them.
What I am wondering is, is there are documentation on the format of the context information output by VALIDATE_GEOMETRY_WITH_CONTEXT, as there are several outputs produced
e.g.
13356 [Element <1>] [Coordinate <4>][Ring <1>]
13349 [Element <1>] [Ring <1>][Edge <6>][Edge <21>]
I can decipher these specific errors, but a definitive reference would be appreciated.
thanks in advance,
Andrew

Answer 1

Hi Andrew,
I know this is hard, but it is a great improvement from earlier, when Oracle didn't report any location information.
The reference for the numbers (13356 or 13349) is the error messages documentation.
ORA-13349: polygon boundary crosses itself
Cause: The boundary of a polygon intersects itself.
Action: Correct the geometric definition of the object.
ORA-13356: adjacent points in a geometry are redundant
Cause: There are repeated points in the sequence of coordinates.
Action: Remove the redundant point.
The rest of the information is an attempt to help you locate where in the geometry the problem was found.
13356 [Element <1>] [Coordinate <4>][Ring <1>]
The first element in SDO_ORDINATE array is the one with the problem
The 4th vertex is a duplicate of the 5th vertex (falls within the specified tolerance so the two coordinates are considered the same).
Ring 1 - The first element is a polygon, and a single polygon can consist of an exterior ring with one or more holes (interior rings). Since this is ring 1, it is the exterior ring associated with the first element. If it was Ring 2, it would be the first hole, ring 3 would be the second hole, and so on.
13349 [Element <1>] [Ring <1>][Edge <6>][Edge <21>]
With this error the first ring (exterior ring) of the first element in the sdo_ordinate_array has edges that self intersect. The edges are edge 6 and edge 21. The edges can be identifed as the 6th and 7th vertices (edge 6) and the 21st and 22nd vertices.
You can use sdo_util.get_vertices to look at coordinate pairs.
There is also sdo_util.remove_duplicate_vertices to get rid of the duplicate vertex errors.
Sometimes I union a geometry with itself to see if Oracle can fix an invalid polygon whose edges intersect (this isn't guaranteed to work because operations on invalid geometries aren't supported), but if it succeeds I look at the input and output geometries together and if I am convinced they are the same then I put the new geometry back into the table.
Hope this helps,
Dan