  This paper gives a brief overview of computation models for data stream
processing, and it introduces a new model for multi-pass processing of multiple
streams, the so-called mp2s-automata. Two algorithms for solving the set
disjointness problem wi th these automata are presented. The main technical
contribution of this paper is the proof of a lower bound on the size of memory
and the number of heads that are required for solvin g the set disjointness
problem with mp2s-automata.
