Multi-News: a Large-Scale Multi-Document Summarization Dataset and Abstractive Hierarchical Model
Table 4: Percentage of n-grams in summaries which do not appear in the input documents , a measure of the abstractiveness, in relevant datasets.
['[BOLD] % novel n-grams', '[BOLD] Multi-News', '[BOLD] DUC03+04', '[BOLD] TAC11', '[BOLD] CNNDM']
We report the percentage of n-grams in the gold summaries which do not appear in the input documents as a measure of how abstractive our summaries are in Table 4. As the table shows, the smaller MDS datasets tend to be more abstractive, but Multi-News is comparable and similar to the abstractiveness of SDS datasets. Grusky et al. (2018) additionally define three measures of the extractive nature of a dataset, which we use here for a comparison.