  In this paper, we introduce \textsc{Yedda}, a lightweight but efficient and
comprehensive open-source tool for text span annotation. \textsc{Yedda}
provides a systematic solution for text span annotation, ranging from
collaborative user annotation to administrator evaluation and analysis. It
overcomes the low efficiency of traditional text annotation tools by annotating
entities through both command line and shortcut keys, which are configurable
with custom labels. \textsc{Yedda} also gives intelligent recommendations by
learning the up-to-date annotated text. An administrator client is developed to
evaluate annotation quality of multiple annotators and generate detailed
comparison report for each annotator pair. Experiments show that the proposed
system can reduce the annotation time by half compared with existing annotation
tools. And the annotation time can be further compressed by 16.47\% through
intelligent recommendation.
