The Italian dependency annotated corpus developed for the CoNLL-X Shared Task

This document illustrates the Italian dependency annotated corpus developed for the CoNLL-X Shared Task (henceforth referred to as ISST-CoNLL). In particular, it provides information on the background resource, the way the CoNLL Italian resource has been designed and developed, and finally documents the adopted annotation scheme. The Italian dependency annotated corpus developed for the CoNLL-2007 Shared Task ISST-CoNLL Abstract. This document illustrates the Italian dependency annotated corpus developed for the CoNLL-2007 Shared Task (henceforth referred to as ISSTCoNLL). In particular, it provides information on the background resource, the way the CoNLL Italian resource has been designed and developed, and finally describes the adopted annotation scheme. This document illustrates the Italian dependency annotated corpus developed for the CoNLL-2007 Shared Task (henceforth referred to as ISSTCoNLL). In particular, it provides information on the background resource, the way the CoNLL Italian resource has been designed and developed, and finally describes the adopted annotation scheme. 1 The background resource The Italian dependency annotated corpus developed for the CoNLL-2007 Shared Task was derived from the Italian Syntactic-Semantic Treebank (ISST), a multi-layered annotated corpus of Italian which represents one of the main outcomes of an Italian national project, SI-TAL, funded by the Italian Ministery of Science and Research (MURST) for the design and development of an integrated suite of tools and resources for Italian Natural Language Processing. The project consortium included companies and computational linguistics sites in Italy which are active with different expertise in the computational linguistics field (ILC-CNR/CPR, Venezia University/CVR, ITC-IRST, “Tor Vergata” University/CERTIA and Synthema). ISST was developed between 1999 and 2001 and is being updated whenever needed. It is worth mentioning here that among the expected uses for ISST there were also training (and/or tuning) of grammars and sense disambiguation systems and the evaluation of language technology systems. For more details see Montemagni et al. (2003a, 2003b) and the web page http://www.ilc. cnr.it/viewpage.php/sez=ricerca/id=874/vers=ing. 1.1 ISST overall architecture ISST has a five-level structure covering orthographic, morpho-syntactic, syntactic and semantic levels of linguistic description. Syntactic annotation is distributed over two different levels: the constituent structure level and the dependency annotation level. The fifth level deals with lexicosemantic annotation, which is carried out in terms of sense tagging of lexical heads (nouns, verbs and adjectives) augmented with other types of semantic information: ItalWordNet is the reference lexical resource used for the sense tagging task. Both syntactic and lexico-semantic annotations refer to the morpho-syntactically annotated text, which in turn is linked to the orthographic file with the text and mark-up of macrotextual organisation (e.g. titles, subtitles, summary, body of article, paragraphs). 1.2 Syntactic annotation in ISST Among the main features of ISST with respect to other treebanks there is the distributed approach to syntactic annotation. In this respect, ISST differs from most treebanks which adopt a unique syntactic representation layer. ISST also differs from multi-level treebanks like the Prague Dependency Treebank (PTD): whereas PTD annotation levels refer respectively to a) the surface dependency relations and b) the underlying sentence structure, ISST syntactic annotation levels are intended to provide orthogonal and independent views of the same surface syntax. None of the ISST syntactic annotation levels presupposes the other; on the other hand combined views of the complementary information contained in them can be provided, e.g. dependency information can be projected onto the constituent structure. The motivations underlying this “double-track” approach to syntactic representation range from language-specific ones (e.g. the syntactically free constituent order and the pro-drop property of Italian) to usage-oriented ones (ISST syntactic annotation levels are intended to be exploitable both in real applications and for research purposes, and to be compatible with different approaches to syntax, either adopted in theoretical or applicative frameworks). 1.3 Corpus composition The ISST corpus consists of 305,547 word tokens reflecting contemporary language use. It includes two different sections: 1) a “balanced” corpus, testifying general language usage, for a total of 215,606 tokens; 2) a specialised corpus, amounting to 89,941 tokens, with texts belonging to the financial domain. The balanced corpus contains a selection of articles from different types of Italian texts, namely newspapers (La Repubblica and Il Corriere della Sera) and a number of different periodicals which were selected to cover a high variety of topics (politics, economy, culture, science, health, sport, leisure, etc.) covering a 10 year time period (1985-1995). The financial corpus includes articles taken from Il Sole-24Ore which were published in 1994. 2 The CoNLL-2007 Shared Task Italian resource: ISST-CoNLL ISST was used as the starting point to build the Italian annotated corpus developed for the CoNLL2007 Shared Task. In particular, ISST-CoNLL was built on top of the morpho-syntactic and syntactic dependency annotation levels through a semi-automatic conversion process cooperatively carried out by ILC-CNR and the Dipartimento di Informatica of the University of Pisa. Conversion was in charge of : a) combining information coming from two different annotation levels b) converting the ISST annotation scheme for dependency annotation into the CoNLL-2007 tabular format. Conversion had to cope with the fact that in ISST dependency relations are expressed in terms of binary relations holding between two lexical heads belonging to major lexical classes only (i.e. nonauxiliary verbs, nouns, adjectives and adverbs): in fact, in ISST information about grammatical words (e.g. determiners, prepositions, auxiliaries) is encoded in terms of features associated with the participants to the relation. This implies that during the conversion process the dependency relations involving grammatical words had to be reconstructed from the ISST original annotation and the already existing dependency relations had to be revised accordingly. This was done semi-automatically by means of several conversion scripts whose output has been manually revised with the help of a graphical annotation tool. Further scripts were run to validate the consistency of the final output. An XML intermediate format was produced in this process, with purpose of preserving original annotations that could not be accomodated in the CoNLL format. For what concerns corpus composition, ISST-CoNLL is a subset of the balanced ISST corpus of 79654 word tokens (of which 65016 were non punctuation tokens) for a total 4162 sentences, corresponding to the Corriere della Sera and periodicals partitions. ISST-CoNLL is copyrighted material which can be used for research purposes only and which cannot be distributed in any original or modified form (see the licence agreement form). 3 ISST-CoNLL annotation