Evaluation and improvements of runtime monitoring methods for real-time event streams

Runtime monitoring is of great importance as a safeguard to guarantee the correctness of system runtime behaviors. Two state-of-the-art methods, dynamic counters and l-repetitive function, were recently developed to tackle the runtime monitoring for real-time systems. While both are reported to be efficient in monitoring arbitrary events, the monitoring performance between them has not yet been evaluated. This article evaluates both methods in depth, to identify their strengths and weaknesses. New methods are proposed to efficiently monitor the many-to-one connections that are abstracted as AND and OR components on multiple inputs. Representative scenarios are used as our case studies to quantitatively demonstrate the evaluations. Both methods are implemented in hardware FPGA. The timing overhead and resource usages of implementing the two methods are evaluated.