These features include lexical bag-of-words features and features based on syntactic parse trees.
while simply adding word embeddings trained using window-based contexts as additional features to existing systems has proven valuable (Turian et al., 2010), more recent studies have focused on how to tune and enhance word embeddings for specific tasks (Bansal et al., 2014;Boros et al., 2014;Chen et al., 2014;Guo et al., 2014; Nguyen and Grishman, 2014) and we continue this line of research for the task of relation classification.