Categorial Dependency Grammars with Iterated Sequences

Some dependency treebanks use special sequences of dependencies where main arguments are mixed with separators. Classical Categorial Dependency Grammars (CDG) do not allow this construction because iterative dependency types only introduce the iterations of the same dependency. An extension of CDG is defined here that introduces a new construction for repeatable sequences of one or several dependency names. The learnability properties of the extended CDG when grammars are infered from a dependency treebank is also studied. It leads to the definition of new classes of grammars that are learnable in the limit from dependency structures.