  In this paper, we propose a new model that is capable of recognizing
overlapping mentions. We introduce a novel notion of mention separators that
can be effectively used to capture how mentions overlap with one another. On
top of a novel multigraph representation that we introduce, we show that
efficient and exact inference can still be performed. We present some
theoretical analysis on the differences between our model and a recently
proposed model for recognizing overlapping mentions, and discuss the possible
implications of the differences. Through extensive empirical analysis on
standard datasets, we demonstrate the effectiveness of our approach.
