  This article presents a discussion on the main linguistic phenomena which
cause difficulties in the analysis of user-generated texts found on the web and
in social media, and proposes a set of annotation guidelines for their
treatment within the Universal Dependencies (UD) framework of syntactic
analysis. Given on the one hand the increasing number of treebanks featuring
user-generated content, and its somewhat inconsistent treatment in these
resources on the other, the aim of this article is twofold: (1) to provide a
condensed, though comprehensive, overview of such treebanks -- based on
available literature -- along with their main features and a comparative
analysis of their annotation criteria, and (2) to propose a set of tentative
UD-based annotation guidelines, to promote consistent treatment of the
particular phenomena found in these types of texts. The overarching goal of
this article is to provide a common framework for researchers interested in
developing similar resources in UD, thus promoting cross-linguistic
consistency, which is a principle that has always been central to the spirit of
UD.
