  Storyline visualizations depict the temporal dynamics of social interactions,
as they describe how groups of actors (individuals or organizations) change
over time. A common constraint in storyline visualizations is that an actor
cannot belong to two different groups at the same time instant. However, this
constraint may be too severe in some application scenarios, thus we generalize
the model by allowing an actor to simultaneously belong to distinct groups at
any point in time. We call this model Storyline with Ubiquitous Actors (SUA).
Essential to our model is that an actor is represented as a tree rather than a
single line. We describe an algorithmic pipeline to compute storyline
visualizations in the SUA model and discuss case studies on publication data.
