Updatable timed automata with one updatable clock  

作　　者：Guoqiang LI Yunqing WEN Shoji YUEN 

机构地区：[1]BASICS, School of Software, Shanghai Jiao Tong University [2]Graduate School of Information Science, Nagoya University

出　　处：《Science China(Information Sciences)》2018年第1期95-108,共14页中国科学（信息科学）（英文版）

基　　金：supported by NSFC-JSPS Bilateral Joint Research Project (Grant No. 61511140100);National Natural Science Foundation of China (Grant Nos. 61472240, 61602224, 91318301)

摘　　要：Updatable timed automata（UTAs） proposed by Bouyer et.al., is an extension of timed automata（TAs） having the extra ability to update clocks in a more elaborate way than simply reset them to zero.The reachability of UTAs is generally undecidable, which can be easily gained by regarding a pair of clocks as updatable counters. This paper investigates a subclass of UTAs by restricting the number of updatable clocks to be one. We will show that（1） the reachability of general UTAs with one updatable clock（UTA1 s）is still undecidable, and（2） that of UTA1 s under diagonal-free constraints is decidable, and the complexity is Pspace-complete. The former is achieved by encoding Minsky machines to the general UTA1 s, where two counters are simulated by the updatable clock. The latter is gained by regarding a region of a UTA1 to be an unbounded digiword, and encoding sets of digiwords that are accepted by a one counter automaton where regions are generated as the value of the counter.Updatable timed automata（UTAs） proposed by Bouyer et.al., is an extension of timed automata（TAs） having the extra ability to update clocks in a more elaborate way than simply reset them to zero.The reachability of UTAs is generally undecidable, which can be easily gained by regarding a pair of clocks as updatable counters. This paper investigates a subclass of UTAs by restricting the number of updatable clocks to be one. We will show that（1） the reachability of general UTAs with one updatable clock（UTA1 s）is still undecidable, and（2） that of UTA1 s under diagonal-free constraints is decidable, and the complexity is Pspace-complete. The former is achieved by encoding Minsky machines to the general UTA1 s, where two counters are simulated by the updatable clock. The latter is gained by regarding a region of a UTA1 to be an unbounded digiword, and encoding sets of digiwords that are accepted by a one counter automaton where regions are generated as the value of the counter.

关 键 词：updatable timed automata one counter automata digiword reachability problem 

分 类 号：TP4[自动化与计算机技术]