Proceedings of the 2nd Workshop on Building and Using Comparable Corpora: from Parallel to Non-parallel Corpora

Research in comparable corpora has been motivated by two main reasons in the language engineering and the linguistics communities. In language engineering, it is chiefly motivated by the need to use comparable corpora as training data for statistical NLP applications such as statistical machine translation or cross-language information retrieval. In linguistics, on the other hand, comparable corpora are of interest themselves in providing intra-linguistic discoveries and comparisons. It is generally accepted in both communities that comparable corpora are documents in one to many languages, that are comparable in content and form in various degrees and dimensions. It was pointed out that parallel corpora are at one end of the spectrum of comparability whereas quasi-comparable corpora are at the other end. We believe that the linguistic definitions and observations in comparable corpora can improve methods to mine such corpora for applications to statistical NLP. As such, it is of great interest to bring together builders and users of such corpora. Parallel corpora are a key resource as training data for statistical machine translation, and for building or extending bilingual lexicons and terminologies. However, beyond a few language pairs such as English- French or English-Chinese and a few contexts such as parliamentary debates or legal texts, they remain a scarce resource, despite the creation of automated methods to collect parallel corpora from the Web. Interest in non-parallel forms of comparable corpora in language engineering primarily ensued from the scarcity of parallel corpora. This has motivated research into the use of comparable corpora: pairs of monolingual corpora selected according to the same set of criteria, but in different languages or language varieties. Non-parallel yet comparable corpora overcome the two limitations of parallel corpora, since sources for original, monolingual texts are much more abundant than translated texts. However, because of their nature, mining translations in comparable corpora is much more challenging than in parallel corpora. What constitutes a good comparable corpus, for a given task or per se, also requires specific attention: while the definition of a parallel corpus is fairly straightforward, building a non-parallel corpus requires control over the selection of source texts in both languages. With the advent of online data, the potential for building and exploring comparable corpora is growing exponentially. Comparable documents in languages that are very different from each other pose special challenges as very often, the non-parallel-ness in sentences can result from cultural and political differences. Following the success of the first workshop on Building and Using Comparable Corpora at LREC 2008 in Marrakech, this second workshop again brings together language engineers as well as linguists interested in the constitution and use of comparable corpora, ranging from parallel to non-parallel corpora. In the larger context of the joint ACL-IJCNLP conference, this time the workshop specifically aimed to solicit contributions from researchers in different geographical regions, in order to highlight in particular the issues with comparable corpora across languages that are very different from each other, such as across Asian and European languages. Research in minority languages is also of particular interest. We are very glad to include papers on languages as varied as Arabic, Chinese, English, French, Japanese, Uyghur and even sign language.