Building a Web Corpus of Czech

Abstract

Large corpora are essential to modern methods of computational linguistics and natural language processing. In this paper, we describe an ongoing project whose aim is to build a largest corpus of Czech texts. We are building the corpus from Czech Internet web pages, using (and, if needed, developing) advanced downloading, cleaning and automatic linguistic processing tools. Our concern is to keep the whole process language independent and thus applicable also for building web corpora of other languages. In the paper, we briefly describe the crawling, cleaning, and part-of-speech tagging procedures. Using a prototype corpus, we provide a comparison with a current corpora (in particular, SYN2005, part of the Czech National Corpora). We analyse part-of-speech tag distribution, OOV word ratio, average sentence length and Spearman rank correlation coefficient of the distance of ranks of 500 most frequent words. Our results show that our prototype corpus is now quite homogenous. The challenging task is to find a way to decrease the homogeneity of the text while keeping the high quality of the data.