We propose a new variant of Tree- Adjoining Grammar that allows adjunc- tion of full wrapping trees but still bears only context-free expressivity. We provide a transformation to context-free form, and a further reduction in probabilistic model size through factorization and pooling of parameters. This collapsed context-free form is used to implement efficient gram- mar estimation and parsing algorithms. We perform parsing experiments the Penn Treebank and draw comparisons to Tree- Substitution Grammars and between dif- ferent variations in probabilistic model de- sign. Examination of the most probable derivations reveals examples of the lin- guistically relevant structure that our vari- ant makes possible.

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