Lexicalized Tree-Adjoining Grammars (LTAG) - ad-teaching.infor...

Cross-Serial Dependencies
Example (Swiss German; Shieber, 1985)
b a b a
. . . das mer em Hans es huus hälfed aastriiche
. . . that we Hans DAT house ACC helped paint
‘. . . that we helped Hans paint the house’
a b a a b a
. . . das mer d’chind em Hans es huus lönd hälfe aastriiche
. . . that we the children ACC Hans DAT house ACC let help paint
‘. . . that we let the children help Hans paint the house’
This can be reduced to the copy language {ww | w ∈ {a, b} ∗ }
which is not context-free.
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