Monitoring Events that Carry Data.

Very early runtime verification systems focused on monitoring what we can refer to as propositional events: just names of events. For this, finite state machines, standard regular expressions, or propositional temporal logics were sufficient formalisms for expressing properties. However, in practice there is a need for monitoring events that in addition carry data arguments. This adds complexity to both the property specification languages, and monitoring algorithms, which is reflected in the many alternative such approaches suggested in the literature. This chapter presents five different formalisms and monitoring approaches that support specifications with data, in order to illustrate the challenges and various solutions.