Structure-Infused Copy Mechanisms for Abstractive Summarization
Table 10: Percentages of source dependency relations (of various types) preserved in the system summaries.
['[BOLD] System', '[BOLD] nsubj', '[BOLD] dobj', '[BOLD] amod', '[BOLD] nmod', '[BOLD] nmod:poss', '[BOLD] mark', '[BOLD] case', '[BOLD] conj', '[BOLD] cc', '[BOLD] det']
Dependency relations. A source relation is considered preserved if both its words appear in the summary. We observe that the models implementing structure-infused copy mechanisms (e.g., “Struct+2Way+Word”) are more likely to preserve important dependency relations in the summaries, including nsubj, dobj, amod, nmod, and nmod:poss. Dependency relations that are less important (mark, case, conj, cc, det) are less likely to be preserved. These results show that our structure-infused copy mechanisms can learn to recognize the importance of dependency relations and selectively preserve them in the summaries.