  We propose an automatic language-independent graph-based method to build
\`a-la-carte article collections on user-defined domains from the Wikipedia.
The core model is based on the exploration of the encyclopaedia's category
graph and can produce both monolingual and multilingual comparable collections.
We run thorough experiments to assess the quality of the obtained corpora in 10
languages and 743 domains. According to an extensive manual evaluation, our
graph-based model outperforms a retrieval-based approach and reaches an average
precision of 84% on in-domain articles. As manual evaluations are costly, we
introduce the concept of "domainness" and design several automatic metrics to
account for the quality of the collections. Our best metric for domainness
shows a strong correlation with the human-judged precision, representing a
reasonable automatic alternative to assess the quality of domain-specific
corpora. We release the WikiTailor toolkit with the implementation of the
extraction methods, the evaluation measures and several utilities. WikiTailor
makes obtaining multilingual in-domain data from the Wikipedia easy.
