Streams are infinite sequences of symbols that are studied by both mathematicians and com- puter scientists. A mathematicians interest in streams may come from viewing them as represen- tations of numbers via expansion in some base p, as symbolic  sequences representing  a dynamical system, or as combinatorial,  or fractal objects. A computer scientist may be interested in streams as representations   of executions of non-terminating  systems (such as operating  systems),  or as streams of data (e.g. Twitter). The research in mathematics and computer science seems to run parallel, but along disjoint tracks. A few connections between the two fields exist via the areas of automata theory and combinatorics, but there is much more to be explored.  The aim of this workshop  was to establish common ground and stimulate collaboration between mathematicians and computer scientists on the topic of streams. We wanted especially to bring together the young researchers of these areas, as they will eventually be setting the future agenda. This was greatly facilitated by the generous funding  we received from the Lorentz Center together with the STAR and DIAMANT clusters. This funding enabled us to provide all young researchers with grants for travel and accommodation.


The workshop consisted of a school week and a workshop week. In the school week, we had 5 tutorials plus 8 short research talks. In the workshop week, we had 5 keynote talks plus 16 research talks. In both weeks, there was ample time for discussion and interaction  between participants, facilitated by scheduled problem  sessions and frequent  coffee breaks. The mix between

mathematics and computer science was about 50/50 both in terms of scheduled talks and in terms of attendance.  The school week had 46 participants of which 1/3 were PhD students.  The second week had 50 participants of which more than 1/4 were PhD students.


All participants  were extremely positive about the event, and we observed a great  deal of interaction,  especially among the younger participants. There were often lively discussions going on in the common room until late in the day, sometimes extending into joint dinners. The problem sessions also resulted  in new collaborations between mathematicians and computer scientists, and we expect publications from these projects over the coming year.


The facilities provided by the Lorentz Center, especially its extremely helpful staff, were crucial in making this event a success.


Joerg Endrullis (VU Amsterdam) Helle Hvid Hansen (RU Nijmegen) Dimitri Hendriks (VU Amsterdam) Charlene Kalle (U. Leiden)

Evgeny Verbitskiy (U. Leiden)