The DEBS challenge was introduced first time in DEBS 2011, since then it also became "grand".
This year it was around football (or soccer for the USA guys) and consisted mainly on aggregations, but also detection of proximity between player and ball, using sensors. There was a lot of interest this year, and 14 submissions. It becomes a "community building" theme. 6 solutions arrived to the final and were invited to present at the conference, a lot of effort has been dedicated, and we saw very nice and creative solutions. The main criteria was performance that had to be measured on a given data-set. In the business meeting I raised some ideas to make it even more interesting, by given "unseen" data at the conference itself, and introduce last minute change in the specification. The conference is now at its last session. Next year - DEBS 2014 is planned to be in IIT Bombay, India.