Threshold Constraints with Guarantees for Parity Objectives in Markov Decision Processes

Raphaël Berthon
ULB
Friday, 10 March, 2017 - 16:00
Salle Solvay (NO, 5th floor)
Threshold Constraints with Guarantees for Parity Objectives in Markov Decision Processes
 
The beyond worst-case synthesis problem was introduced recently by Bruyère et al. in 2014: it aims at building system controllers that provide strict worst-case performance guarantees against an antagonistic environment while ensuring higher expected performance against a stochastic model of the environment. Our work extends this framework and follow-up papers, which focused on quantitative objectives, by addressing the case of ω-regular conditions encoded as parity objectives, a natural way to represent functional requirements of systems.
 
We build strategies that satisfy a main parity objective on all plays, while ensuring a secondary one with sufficient probability. This setting raises new challenges in comparison to quantitative objectives, as one cannot easily mix different strategies without endangering the functional properties of the system. We establish that, for all variants of this problem, deciding the existence of a strategy lies in NP intersection coNP, the same complexity class as classical parity games. Hence, our framework provides additional modeling power while staying in the same complexity class. 
 
This is a joint work of Raphaël Berthon, Mickaël Randour and Jean-François Raskin