Further expansion of the C roatian W ord N et (2018)

Abstract: In this paper a semi-automatic procedure for the expansion of the Croatian Wordnet (CroWN) is presented. An English-Croatian dictionary was used in order to translate monosemous PWN 3.0 English variants. The precision values of the automatic process is low (about 30%), but the results proved valuable for the enlargment of CroWN. After manual validation, 10,884 new synset-variant pairs were added to CroWN, achieving a total of 62,075 synset-variant pairs.

## introduction the building of the croatian wordnet has begun in 2004 at the institute of linguistics, faculty of humanities and social sciences, university of zagreb. the croatian wordnet is a lexical database built through the expand model @xcite . the development of the croatian wordnet (crown) can be divided into two major phases (crown 1.0 vs. crown 2.0 / 3.0). both versions are available for download and on-line queries. crown 1.0. @xcite was built completely manually. the main objective in this phase of the project was to translate and adapt the socalled basic concept sets extracted from the wn version 1.5 and used in the multilingual projects eurowordnet (ewn) and balkanet (bn). for each synset a meaning definition was translated and adapted. each synset in crown 1.0 is also accompanied by one or more examples of contextual usage. synsets contain literals or synset variant pairs of the same part of speech. crown 1.0 comprises 10,000 synsets. 8500 of these are from the basic concept sets of ewn and bn. approximately 1500 noun synsets were added using the same procedure. although rich in information and data, crown 1.0 is a relatively small resource. in order to make it more useful in various nlp tasks, the second phase of the project was primarily oriented toward its enlargement. crown 2.0 and crown 3.0 @xcite were built by using different automatic approaches. these versions of the lexicon are the result of joint work between two research teams from zagreb and barcelona. crown 2.0 and 3.0 contain only synset-variant pairs in croatian, i.e. meaning definitions and examples of contextual usage have not been translated (yet). crown 2.0 and crown 3.0 are available at the open multilingual wordnet website foot_0 . in this paper we present a semi-automatic method that was used for further expanding of crown, i.e. for the creation of its version 3.1. the paper is structured as follows: in section 2 we describe the algorithms and procedures applied in the creation of versions 2.0 and 3.0 and provide some statistics regarding the number of synsets, pos distribution etc. section 3 deals with the procedure and resources applied in the experiment presented in this paper. in section 4 results are discussed as well as advantages or potential disadvantages of the method applied here. section 4 brings concluding remarks and the outline of future work. ## versions of the croatian wordnet at this time, crown is the only resource for croatian that deals with lexical semantics and also provides multilingual links to similar resources via the open multilingual wordnet project. as mentioned, crown 2.0 and crown 3.0 are the result of joint work between two research teams from zagreb and barcelona. the 2.0 version of the crown was developed using the wn-toolkit foot_1 @xcite , a set of python programs for the automatic creation of wordnets following the expand model. the wn-toolkit implements 3 different strategies for wordnet creation: 1. dictionary-based strategy -bilingual dictionaries are used to translate english variants associated with each synset. the strategy can deal only with monosemous english variants, i.e. variants associated with a single synset. 2. babelnet-based strategy -the data from the ba-belnet @xcite file was extracted in order to obtain the data for crown. 3. parallel-corpus-based strategy -in order to extract a target language wordnet, at least the english part of a parallel corpus should be sense tagged with pwn synsets. as such resources are rare and not easily available, two additional procedures were used for the creation of such a corpus: machine translation of sense-tagged corpora and automatic sense tagging of the english part of the parallel corpus. another line of work in crown 2.0 was oriented towards the enlargement of verbal synsets in crown. in crown 1.0 nouns make up almost 75 % of the whole lexicon (7391 noun synsets vs. 2318 verb synsets). the goal was to make crown a more balanced and representative resource for croatian by enlarging the number of verbs. for this purpose we used croderiv @xcite foot_2 , a large derivational database of croatian verbs. the data was extracted and matched with pwn automatically. a more detailed account of the procedure and results is given in @xcite . as in all other procedures described here, all candidates for synsets were manually checked and corrected if necessary. taking into account that every automatic processing of data is followed by a manual revision, all procedures discussed here can be considered as semi-automatic. with all these strategies we reached the 70.63 % of the core synsets @xcite ). finally, we manually populated crown 2.0 with the remaining 1,456 synsets, thus reaching 100 % of the core wordnet. for the creation of the version 3.0 we used a new version of the wn-toolkit. it implements several strategies for mapping lexical resources (wikipedia, wiktionary and omegawiki). an extensive account of this procedure is given in @xcite .