2015/10/12 by Lorenzo Clemente, Paweł Parys, Clemente, Lorenzo +5
Computer Science · #D.1.1 #D.2.4 #F.1.1 #F.3.1 #F.4.1 #FOS: Computer and information sciences #Formal Languages and Automata Theory (cs.FL) #cs.FL
paper · pdf · doi:10.48550/arxiv.1510.03278
full technical report of FST-TCS'15 paper
arxiv created 2015/10/12 · arxiv updated 2015/10/13
We define a new class of pushdown systems where the pushdown is a tree instead of a word. We allow a limited form of lookahead on the pushdown conforming to a certain ordering restriction, and we show that the resulting class enjoys a decidable reachability problem. This follows from a preservation of recognizability result for the backward reachability relation of such systems. As an application, we show that our simple model can encode several formalisms generalizing pushdown systems, such as ordered multi-pushdown systems, annotated higher-order pushdown systems, the Krivine machine, and ordered annotated multi-pushdown systems. In each case, our procedure yields tight complexity.