I. Introduction
In peer production communities, quality assessment is indispensable. Take Wikipedia for an example, assessing article quality is a traditional and important task, which, in practice, can assistant readers to distinguish high-quality content from massive information and, at the same time, instruct editors to improve poor-quality content. On Wikipedia, there are two methods for users to acquire article quality information. One is the ‘Featured articles’
https://en.wikipedia.org/wiki/Wikipedia:Featured_articles
, which are officially regarded as the best articles. However, on English Wikipedia, only 0.1% articles are featured. The other way is ‘WikiProject assessment’https://en.wikipedia.org/wiki/Category:Wikipedia_1.0_assessments
in which WikiProject members rate articles with 7-class quality labels. However, this assessment is voluntary. When and how often to assess articles totally depend on users, and thus the tagged quality label is probably out-of-date and unreliable. Therefore, an automatic article quality assessment is necessary.