This document discusses mining frequent closed unlabeled rooted trees in data streams. It introduces the problem of finding frequent closed trees in a data stream of unlabeled rooted trees. It describes some of the challenges of data streams, including that the sequence is potentially infinite, there is a high amount of data requiring sublinear space, and a high speed of arrival requiring sublinear time per example. The document outlines an approach using ADWIN, an adaptive sliding window algorithm, to detect concept drift and adapt the window size accordingly.