Runtime monitoring is a general approach to verifying system properties at runtime by comparing system events against a specification formalizing which event sequences are allowed. We present a runtime monitoring algorithm for a safety fragment of metric first-order temporal logic that overcomes the limitations of prior monitoring algorithms with respect to the expressiveness of their property specification languages. Our approach, based on automatic structures, allows the unrestricted use of negation, universal and existential quantification over infinite domains, and the arbitrary nesting of both past and bounded future operators. Furthermore, we show how to use and optimize our approach for the common case where structures consist of only finite relations, over possibly infinite domains. We also report on case studies from the domain of security and compliance in which we empirically evaluate the presented algorithms. Taken together, our results show that metric first-order temporal logic can serve as an effective specification language for expressing and monitoring a wide variety of practically relevant system properties.

A robot testbed for writing Chinese and Japanese calligraphy characters is presented. Single strokes of the calligraphy characters are represented in a database and initialized with a scanned reference image and a manually chosen initial drawing spline. A learning procedure uses visual feedback to analyze each new iteration of the drawn stroke and updates the drawing spline such that every subsequent drawn stroke becomes more similar to the reference image. The learning procedure can be performed either in simulation, using a simple brush model to create simulated images of the strokes, or with a real robot arm equipped with a calligraphy brush and a camera that captures images of the drawn strokes. Results from both simulations and experiments with the robot arm are presented.

We show the practical feasibility of monitoring complex security properties using a runtime monitoring approach for metric first-order temporal logic. In particular, we show how a wide variety of security policies can be naturally formalized in this expressive logic, ranging from traditional policies like Chinese Wall and separation of duty to more specialized usage-control and compliance requirements. We also explain how these formalizations can be directly used for monitoring and experimentally evaluate the performance of the resulting monitors.

We introduce a novel approach to the runtime monitoring of complex system properties. In particular, we present an online algorithm for a safety fragment of metric first-order temporal logic that is considerably more expressive than the logics supported by prior monitoring methods. Our approach, based on automatic structures, allows the unrestricted use of negation, universal and existential quantification over infinite domains, and the arbitrary nesting of both past and bounded future operators. Moreover, we show how to optimize our approach for the common case where structures consist of only finite relations, over possibly infinite domains. Under an additional restriction, we prove that the space consumed by our monitor is polynomially bounded by the cardinality of the data appearing in the processed prefix of the temporal structure being monitored.