  More than 30 years after Cronin's seminal paper on "the need for a theory of
citing" (Cronin, 1981), the metrics community is once again in need of a new
theory, this time one for so-called "altmetrics". Altmetrics, short for
alternative (to citation) metrics -- and as such a misnomer -- refers to a new
group of metrics based (largely) on social media events relating to scholarly
communication. As current definitions of altmetrics are shaped and limited by
active platforms, technical possibilities, and business models of aggregators
such as Altmetric.com, ImpactStory, PLOS, and Plum Analytics, and as such
constantly changing, this work refrains from defining an umbrella term for
these very heterogeneous new metrics. Instead a framework is presented that
describes acts leading to (online) events on which the metrics are based. These
activities occur in the context of social media, such as discussing on Twitter
or saving to Mendeley, as well as downloading and citing. The framework groups
various types of acts into three categories -- accessing, appraising, and
applying -- and provides examples of actions that lead to visibility and
traceability online. To improve the understanding of the acts, which result in
online events from which metrics are collected, select citation and social
theories are used to interpret the phenomena being measured. Citation theories
are used because the new metrics based on these events are supposed to replace
or complement citations as indicators of impact. Social theories, on the other
hand, are discussed because there is an inherent social aspect to the
measurements.
