#25 Concept definition robust error messages

[Anonymous]

If you enter the following concept definition

A Waterfall is anything that:
is a kind of Topographic Object;
is a part of exactly one River or Stream;
is located at exactly one Cliff or Slope or Escarpment;
has a Current.

ROO doesn't recognize the sentence at all and gives no helpful error message. To correct the sentence it is enough to remove the 'a' in 'is a part of exactly ...'.
It would be nice if the rabbit parser would provide better errror messages, especially when the error is hard to spot as in this case.