the problems could be broken down to missing or in-
correct values as well as spelling errors. As a pre-
processing step for this design study, all singular or
oddly appearing values were manually inspected and,
if needed, corrected by inspecting the publication.
Also, duplicates were semi-automatically discovered
and manually removed from the pool.
On basis of the, now reliably “cleaned”, data set,
it was time to investigate whether or not all the re-
quirements from Section 3 could be reliably backed
by data. The requirement R1 should be easy to ob-
tain, since the needed data is directly included in the
data set. This also applies to R3 and R4. Since R5
forms no requirement in terms of the data, it also has
no consequences for the preprocessing step. In terms
of R2, some preprocessing was involved to obtain the
needed data. In an automated process, all authors of
each publication were categorized with respect to the
university structure. Afterwards, a publication was
additionally marked in the following way as:
institute internal, if only authors from the same in-
stitute contributed to the publication.
department internal, if all authors of the publica-
tion belong to the same department, but at least
two different institutes are involved.
interdisciplinary, if authors of at least two different
departments are involved but no external authors.
external, if the publication features at least one ex-
ternal author.
For the strategic thoughts of the investigated core
users, this intersection-free partition was important
and explicitly desired. However, this can differ if
other focus points are tackled in the related use cases.
It is also important to note, that in the structure of
the investigated university, research groups may be-
long to different institutes or even two or more depart-
ments. With respect to this structural feature, publi-
cations were for example marked as interdisciplinary
if authors from at least two research groups were in-
volved and one research group belonged to at least
one department the other research group did not be-
long to.
6.2 General Procedure
In general, the user-centered part of the design study
was performed in an iterative fashion on basis of rapid
prototyping. The six members of the stakeholder
group were initially confronted with simple sketches
of design ideas. Feedback was steadily integrated into
the development of new prototypes, leading to a flow
of artifacts with increasing complexity, functionality,
and closeness to the practical working prototype.
Although the communication with the users was
mainly based on digital artifacts, initial sketches were
done with pen and paper in sketching sessions (Green-
berg et al., 2011; Walny et al., 2015), allowing for
more freedom and creativity. This changed over time
for more preciseness to digital pictures and pseudo-
animations. In the late iterations, web-based mock-
ups and prototypes were used, implemented on ba-
sis of Data-driven Documents (D3) (Bostock et al.,
2011), as also the final prototype.
6.3 Layout
All experts agreed that the final tool should rely on
keyboard and mouse as interaction mechanisms and
should use standard monitors as display devices (R5).
Still, we also tried to keep in mind mobile friendli-
ness, should future requirements arise in this direc-
tion. However, this also heavily influenced our deci-
sion for a standard two-dimensional and rectangular
layout of the desired design.
Since the two main dimensions for nearly all prac-
tical questions and usage scenarios are the number
of publications and the time dimension (R3), these
two also emerged in the design process as dimensions
to map to the two-dimensional design space. Hav-
ing fixed this setting, there still do exist many differ-
ent visualization methods for time-oriented discrete
data. A survey was recently presented by Brehmer et
al. (Brehmer et al., 2017). However, after very short
discussion it was clear, that the optimal setting was
to put the time dimension from left to right, the nat-
ural dextrograde process flow for Europeans, and the
number of publications to the vertical axis.
This design decision and a thorough review of vi-
sualization methods for time-oriented data (Aigner
et al., 2007; Aigner et al., 2011) let to the concept
of visualizing the amount of publications in a stream
graph (R1, R3), as proposed by Havre et al. (Havre
et al., 2000; Byron and Wattenberg, 2008). With this
concept there are at least two additional degrees of
freedom involved, the type of interpolation between
the discrete years and the the interpolation with re-
spect to the publications axis. Interpolating the time
axis is basically trading accuracy for visual appeal. A
comparison of the three supported approaches (con-
stant, linear, and polygonal interpolation) is presented
in Figure 1. Since none of the approaches is optimal
for all different usage scenarios, the prototype allows
for switching between them, with polygonal interpo-
lation being the default setting.
Also for visualizing the publications axis, there
are several different possibilities, from which we have
identified three possibilities that have their eligibility
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