This document describes how to use these tools to build a parallel corpus (for a specific language pair) based on article titles across languages in Wikipedia.
Wikipedia publishes database dumps of their content periodically. To run these scripts you need two files per language pair: the base per-page data, which includes article IDs and their titles in a particular language (ending with -page.sql.gz) and the interlanguage link records (file ends with -langlinks.sql.gz). To find these files, go to the Wikimedia Downloads page and find the database dump for the Wikipedia in one of the languages in the pair (the smaller one is recommended since it will make processing faster). The database backup are named by pairing the ISO 639 code with the word wiki. For example, if you want to build an Arabic-English corpus, you should download the relevant files from the arwiki dump, since there are fewer Arabic articles than English articles.
Example:
wget http://dumps.wikimedia.org/arwiki/20140831/arwiki-20140831-page.sql.gz
wget http://dumps.wikimedia.org/arwiki/20140831/arwiki-20140831-langlinks.sql.gz
To extract the parallel corpus run the following where the first command line argument is the ISO 639 code of the target language and the second argument is the (path) prefix of the database dump files.
Example:
./build-corpus.sh en arwiki-20140831 > titles.txt
If one of the languages in the pair uses a specific Unicode range, you can easily filter out lines that do not contain such characters. Example filters for a few scripts are included in the filters/ directory.
For example, the following will filter out pairs that do not contain at least one Perso-Arabic character:
./build-corpus.sh en arwiki-20140831 | ./filters/filter-perso-arabic.pl > titles.txt
It is recommended that you have the uconv tool (International Components for Unicode) installed since it is used to normalize Unicode characters.