Spurious ambiguity is a problem in transition-based dependency parsing using static oracle in which there is more than one sequence of transitions leading to a gold parse. According to Goldberg et al. (2012):
Most transition systems, including the arc-eager and arc-standard systems described in Nivre (2003, 2004), exhibit spurious ambiguity and map several sequences to the same gold tree.
Arc-standard transition system
Ambiguity when a head node links to its left and right side (a <- b -> c). There are two sequences leading to this tree structure:
- S S TODO
- S S ...
Arc-eager transition system
Shift-reduce ambiguity: <Shift Left-arc Reduce> and <Reduce Shift Left-arc> lead to the same tree