Stream-based Monitors for Real-time Properties

Hazem Torfah

In stream-based runtime monitoring, streams of data, called input streams, which involve data collected from the system at runtime, are translated into new streams of data, called output streams, which define statistical measures and verdicts on the system based on the input data. The advantage of this setup is an easy-to-use and modular way for specifying monitors with rich verdicts, provided with formal guarantees on the complexity of the monitor.
In this tutorial, we give an overview of the different classes of stream specification languages, in particular those with real-time features. With the help of the real-time stream specification language RTLola, we illustrate which features are necessary for the definition of the various types of real-time properties and we discuss how these features need to be implemented in order to guarantee memory efficient and reliable monitors. To demonstrate the expressive power of the different classes of stream specification languages and the complexity of the different features, we use a series of examples based on our experience with monitoring problems from the areas of unmanned aerial systems and telecommunication networks.

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