From attention to citation: What are altmetrics and how do they work?

Scholarly and social impacts of scientific publications could be measured by various metrics, including article usage, Mendeley readership and Altmetric scores, etc. But what is the relationship amongst the different metrics? Previous studies show there is low correlation between altmetrics and citation, but how do altmetrics compare to other metrics? Xianwen Wang and his colleagues recently conducted a study to answer this question.