 
Summary: Streaming Transducers for Algorithmic Verification
of Singlepass Listprocessing Programs
Rajeev Alur
University of Pennsylvania
alur@cis.upenn.edu
Pavol Cern´y
IST Austria
pavol.cerny@ist.ac.at
Abstract
We introduce streaming data string transducers that map input data
strings to output data strings in a single lefttoright pass in linear
time. Data strings are (unbounded) sequences of data values, tagged
with symbols from a finite set, over a potentially infinite data do
main that supports only the operations of equality and ordering. The
transducer uses a finite set of states, a finite set of variables ranging
over the data domain, and a finite set of variables ranging over data
strings. At every step, it can make decisions based on the next in
put symbol, updating its state, remembering the input data value in
its data variables, and updating datastring variables by concatenat
ing datastring variables and new symbols formed from data vari
