Foundations for Query-based Runtime Monitoring of Temporal Properties over Runtime Models

Abstract

In model-driven engineering, runtime monitoring of systems with complex dynamic structures is typically performed via a runtime model capturing a snapshot of the system state: the model is represented as a graph and properties of interest as graph queries which are evaluated over the model online. For temporal properties, history-aware runtime models encode a trace of timestamped snapshots, which is monitored via temporal graph queries. In this case, the query evaluation needs to consider that a trace may be incomplete, thus future changes to the model may affect current answers. So far there is no formal foundation for query-based monitoring over runtime models encoding incomplete traces.In this paper, we present a systematic and formal treatment of incomplete traces. First, we introduce a new definite semantics for a first-order temporal graph logic which only returns answers if no future change to the model will affect them. Then, we adjust the query evaluation semantics of a querying approach we previously presented, which is based on this logic, to the definite semantics of the logic. Lastly, we enable the approach to keep to its efficient query evaluation technique, while returning (the more costly) definite answers.