To some extent, this hope was validated through a number of works at the time, mostly involving machine translation applications, and constraining in more or less explicit ways the specification of r (van Noord, 1990).
for the non-statistical approaches to parsing then strongly dominant, robustness was an issue: a parser had to either accept or reject a given input x, with no intermediary options, and in order to be able to parse actual utterances, with all their empirical diversity, parsers had to be rather tolerant.