## Random Allocations and Urn Models

My interest on random allocations is not recent, and was revived in the last years by the need for analyzing some random generation algorithms, for which "waiting-time models" turned out to be well-suited:

- analyzing the performance of an algorithm for random Boltzman generation of Hadamard product leads to a boys-and-girls birthday problem (with O. Bodini and O. Roussel, when both were at Paris 6).

- a random generation algorithm for ARN sequences leads to a Coupon Collector model with unequal probabilities (with Y. Ponty at LIX).

Older results deal with identifying classes of models (often related to database modelization, or to a learning problem) that are amenable to a uniform treatment. They often lead to so-called "occupancy urn models", i.e. models where a set of balls are thrown into a sequence of urns and the question is, e.g., the distribution of the number of empty urns. Some of these results are static, some are « semi-dynamic » in the sense that queries and insertions, but not deletions, are allowed, and some are fully dynamic and allow for deletions.