Adding Time to Pushdown Automata
  In this tutorial, we illustrate through examples how we can combine two classical models, namely those of pushdown automata (PDA) and timed automata, in order to obtain timed pushdown automata (TPDA). Furthermore, we describe how the reachability problem for TPDAs can be reduced to the reachability problem for PDAs. 
Parosh Aziz Abdulla (Uppsala University, Sweden), Mohamed Faouzi Atig   (Uppsala University, Sweden), Jari Stenman (Uppsala ...
cs.LO cs.FL