  A new unequal probability sampling method is proposed. This method is
sequential. The decision to select or not each unit is made based on the order
in which the units appear. A variant of this method allows selecting a sample
from a stream. At each step, the decision to take the units successively
according to the order of appearance in the stream is made. This method
involves using a sliding window that is as small as possible. The method also
allows the sample to be spread and even the level of spreading to be adjusted.
