Since a whiteboard is much more a visual thing, I imagine the spec should spend a lot of space defining the visual elements like specifying the control points of the Beizer curves because where a line is drawn and what it overlaps matters a lot on a whiteboard.
But to be a total downer, this spec looks like an extremely rudimentary graph file format, of which there are already like a hundred and all define more visual aspects than this spec.
From my Analysis, GraphML, although specified in XML, seems to be one of the most widely used exchange formats, especially with the yWorks extensions for yEd.
But to be a total downer, this spec looks like an extremely rudimentary graph file format, of which there are already like a hundred and all define more visual aspects than this spec.