ST_Simple should return false with duplicate points

[kneufeld]

The OGS specs state: "has no anomalous geometric points, such as self intersection or self tangency" and "is simple if it does not pass through the same point twice". (2.1.5)

The SQL/MM specs state: "is not simple if any interior point has the same location as another interior point or a point on the boundary" (4.1.4)

So, by definition then, this should return false.

select st_issimple(
  'LINESTRING(0 0, 1 1, 1 1)'::geometry
);
 st_issimple 
-------------
 t
(1 row)

[strk]

They talk about points, not vertices. Listing the same vertex twice could be just seen as a redundancy but doesn't change the point set defined by the line.

What do other spatial database return ?

[pramsey]

I agree with strk, the language is the language of spatial stuff, not structural stuff.