Timed Automata Semantics for Analyzing Creol

We give a real-time semantics for the concurrent, object-oriented modeling language Creol, by mapping Creol processes to a network of timed automata. We can use our semantics to verify real time properties of Creol objects, in particular to see whether processes can be scheduled correctly and meet their end-to-end deadlines. Real-time Creol can be useful for analyzing, for instance, abstract models of multi-core embedded systems. We show how analysis can be done in Uppaal.

💡 Research Summary

The paper presents a rigorous real‑time semantics for Creol, an object‑oriented concurrent modeling language, by translating Creol processes into a network of timed automata. The authors define a systematic mapping that preserves Creol’s high‑level constructs—method calls, asynchronous message passing, await and delay statements—while encoding their temporal behavior as clock constraints, guards, and invariants in timed automata. Each Creol object becomes an automaton module, each method is represented as a sub‑automaton, and inter‑object communication is modeled via channel synchronizations that can carry explicit transmission delays. The mapping also captures scheduling policies such as priority‑based selection by influencing transition choices.

Once translated, the timed‑automata network is expressed in the Uppaal modeling language, allowing the use of Uppaal’s model‑checking engine to verify two primary classes of properties: (1) schedulability, i.e., the absence of deadlocks and the ability of all processes to progress, and (2) deadline compliance, i.e., that end‑to‑end execution of specified tasks finishes within given time bounds. The authors illustrate the approach with a case study resembling a multi‑core embedded system: two Creol objects exchange messages, each with distinct deadlines (10 ms and 15 ms). After translation, Uppaal verifies the TCTL formulas “A