  In collaboration with the Observatories of Palermo and Rome and the SAX-SDC
we are constructing a multi-site interactive archive system featuring specific
analysis tools. In this context we developed a detection algorithm based on the
Wavelet Transform (WT) and performed a systematic analysis of all ROSAT-HRI
public data (~3100 observations +1000 to come). The WT is specifically suited
to detect and characterize extended sources while properly detecting point
sources in very crowded fields. Moreover, the good angular resolution of HRI
images allows the source extension and position to be accurately determined.
This effort has produced the BMW (Brera Multiscale Wavelet) catalogue, with
more than 19,000 sources detected at the ~4.2sigma level. For each source
detection we have information on the position, X-ray flux and extension. This
allows for instance to select complete samples of extended X-ray sources such
as candidate clusters of galaxies or SNR's. Details about the detection
algorithm and the catalogue can be found in Lazzati et al. (1999), Campana et
al. (1999) and Panzera et al. (2001). Here we shall present an overview of
first results from several undergoing projects which make use of the BMW
catalogue.
