2 Training transition-based parsers In transition-based parsing (Nivre, 2003), dependency trees are built incrementally, in a shiftreduce manner: to parse a sentence, a sequence of transitions (the derivation) is applied on the internal state of the parser (the configuration), consisting typically in a stack and a buffer of unprocessed words.
formally, if each configuration is associated with a UAS max , the maximum UAS value that can be achieved by any of its successor derivations, then the action cost is defined as the differ-ence between the current UAS max and the future UAS max (once the corresponding action has been applied).