Even if all f -structures are transferred from the same linguistically rich source, and all generated strings are grammatical, a reduction in error rate of around 50% relative to the upper bound can be achieved by stochastic selection.
a comparison between transfer runs with and without perfect disambiguation of the original string shows a decrease of about 5% in F-score, and of only .1 points for summarization quality when transferring from packed parses instead of from the manually selected parse.