  Stream-based runtime monitors are used in safety-critical applications such
as Unmanned Aerial Systems (UAS) to compute comprehensive statistics and
logical assessments of system health that provide the human operator with
critical information in hand-over situations. In such applications, a visual
display of the monitoring data can be much more helpful than the textual alerts
provided by a more traditional user interface. This visualization requires
extensive real-time data processing, which includes the synchronization of data
from different streams, filtering and aggregation, and priorization and
management of user attention. We present a visualization approach for the
\rtlola monitoring framework. Our approach is based on the principle that the
necessary data processing is the responsibility of the monitor itself, rather
than the responsibility of some external visualization tool. We show how the
various aspects of the data transformation can be described as RTLola stream
equations and linked to the visualization component through a bidirectional
synchronous interface. In our experience, this approach leads to highly
informative visualizations as well as to understandable and easily maintainable
monitoring code.

Formal Languages and Automata Theory