This simple grammar illustrates the problem: grammar problem; start : description ' ' body; description :'des' SEP ID+; body :'body' SEP ID+; SEP : ':'; ID : 'a'..'z'; When trying to parse the following string: des:problem body:thisbodyisaproblem I get a no viable alternative exception. Apparently this happens because the string 'body', which is part of the body-rule also appears as a substring of 'thisbodyisaproblem'. As a counterexample the following string causes NO problems: des:problem body:thisisaproblem Generally the problem occurs if either 'des' or 'body' appears in the text matched by I   More>>

			

			grammar problem;
			

			start  : description ' ' body;
			

			description :'des' SEP ID+;
			

			body  :'body' SEP ID+;
			

			SEP  : ':';
			

			ID   : 'a'..'z';