Semantic Role Labeling with Associated Memory Network
Table 5: Ablations about distance on CoNLL-2009 English development set. ED means edit distance, WMD means word moving distance, SD means SIF distance, RD means random distance.
['System', 'P', 'R', 'F1']
All models use average method for label merging, and the memory size m is set to 4. All the distance calculating methods have surpassed the base model, showing that the proposed AMN is effective. Note that even the random distance model performs better than the base model, with an improvement of 0.3% in F1 score, which shows that the proposed AMN can effectively extract useful information from even poorly related sentences. Besides, associated sentence selection methods based on word embeddings like WMD and SD have similar performance with random distance (RD), which shows simple word embedding may not be good enough signal indicator to measure semantic structure similarity in SRL task. On the contrary, we may also try to explain why even the random distance selection may work to some extent. As sentences always have core arguments label such as A0, A1 and A2, associated sentences even from random selection may also have such labels, which makes them helpful to enhance SRL over these labels. This may explain why our model with randomly selected associated sentences can distinguish core arguments better.