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Enriching the Venice Italian Treebank with Dependency and Grammatical Relations

In this paper we propose a rule-based approach to extract dependency and grammatical functions from the Venice Italian Treebank, a Treebank of written text with PoS and constituent labels consisting of 10,200 utterances and about 274,000 tokens. As manual corpus annotation is expensive and time-consuming, we decided to exploit this existing constituency-based Treebank to derive dependency structures with lower effort. After describing the procedure to extract heads and dependents, based on a head percolation table for Italian, we introduce the rules adopted to add grammatical relation labels. To this purpose, we manually relabeled all non-canonical arguments, which are very frequent in Italian, then we automatically labeled the remaining complements or arguments following some syntactic restrictions based on the position of the constituents w.r.t to parent and sibling nodes. The final section of the paper describes evaluation results. Evaluation was carried out in two steps, one for dependency relations and one for grammatical roles. Results are in line with similar conversion algorithms carried out for other languages, with 0.97 precision on dependency arcs and F-measure for the main grammatical functions scoring 0.96 or above, except for obliques with 0.75.