  Intelligent technologies, in particular systems to promote health and
well-being, are inherently centered around the human being, and they need to
interrelate with human activities at their core. While social sciences provide
angles to study such activities, e.g., within the framework of
cultural-historical activity theory, there is no formal approach to give an
account of complex human activities from a Knowledge Representation and
Reasoning (KR) perspective. Our goal is to develop a logic-based framework to
specify complex activities that is directly informed by activity theory. There,
complex activity refers to the process that mediates the relation between a
subject and some motivating object which in turn generates a hierarchy of goals
that direct actions. We introduce a new temporal logic to formalise key
concepts from activity theory and study various inference problems in our
framework. We furthermore discuss how to use Answer-Set Programming as a KR
shell for activity reasoning that allows to solve various reasoning tasks in a
uniform way.
