tation of the storage technology
(<tt>TTree</tt>) and the data representation (binned vs unbinned) were
intertwined.
<br><br>
Starting with version 3.00, the class structure has been
rearranged: Now classes <tt>RooDataSet</tt> and <tt>RooDataHist</tt> inherit directly
from class <tt>RooAbsData</tt>, and class <tt>RooAbsData</tt> now owns an object that
inherits from <tt>RooAbsDataStore</tt> that implements the storage of the
data. This new class structure allows multiple data storage implementations to
be a