Natural Language Understanding Wiki

SwapStandard is a transition system proposed by Nivre (2009a)[1] to deal with non-projective tree. Its transitions include SHIFT, LEFT-ARC, RIGHT-ARC just as arc-standard and a new transition SWAP which move the second-topmost element of the stack to the top of the buffer. SWAP effectively reorders words, therefore transform non-projective trees into projective tree, on-the-fly.

Nivre (2009a)[1] proposes an eager static oracle for SwapStandard. Another paper in the same year proposed a lazy oracle which helps train faster and more accurate parser (Nivre, 2009b)[2]. Björkelund & Nivre (2015)[3] designed a minimum-swapping static oracle and a dynamic oracle for the transition system.

Transition system[]

Lazy static oracle[]


  1. 1.0 1.1 Joakim Nivre. 2009. Non-projective dependency parsing in expected linear time. In Proceedings of ACLIJCNLP.
  2. Joakim Nivre, Marco Kuhlmann, and Johan Hall. 2009. An improved oracle for dependency parsing with online reordering. In Proceedings of the 11th International Conference on Parsing Technologies (IWPT’09), pages 73–76, Paris, France, October. Association for Computational Linguistics.
  3. Björkelund, Anders, and Joakim Nivre. "Non-Deterministic Oracles for Unrestricted Non-Projective Transition-Based Dependency Parsing." Proceedings of the 14th International Conference on Parsing Technologies. 2015.