WKT number format inconsistent?

Question

The WKT specification allows both period and comma to be the decimal separator in floating-point numbers (section 7.2.1):

<decimal point> ::= <period> | <comma>

However, a comma could result in ambiguous WKT representations. In this example, the polygon is specified with five points, but the WKT could also be parsed as having three points:

POLYGON((0 0,0 1,1 1,1 0,0 0))

I'm assuming that nobody deliberately uses , as decimal separator, but is that really true?

Is there any reason to try to parse numbers in WKT with ,? Or shouly I assume that the specification is just buggy?

Answer 1

Because the coordinate pairs must be separated with a comma, and whitespace is treated as a separator between numbers in a coordinate pair, such ambiguities can be easily worked out by the parser.

(I personally think this is an example of something that could and should be internationally standardized - but then again, I'm also an American who has trouble with the metric system.)

Answer 2

POLYGON((0 0,0 1,1 1,1 0,0 0)) 

is not ambiguous, because the number of values for a point cannot be 3 (that would be POLYGON M or POLYGON Z).

That said, at least SpatiaLite doesn't support comma as a decimal separator. I didn't try other applications.