  X-ray emitting features originating from the interaction of supernova shock
waves with small interstellar gas clouds are revealed in many X-ray
observations of evolved supernova remnants (e.g. Cygnus Loop and Vela), but
their interpretation is not straightforward.
  We develop a self-consistent method for the analysis and interpretation of
shock-cloud interactions in middle-aged supernova remnants, which can provide
the key parameters of the system and the role of relevant physical effects like
the thermal conduction, without the need to run ad-hoc numerical simulations
and to bother of morphology details.
  We explore all the possible values of the shock speed and cloud density
contrast relevant to middle-aged SNRs with a set of hydrodynamic simulations of
shock-cloud interaction, including the effects of thermal conduction and
radiative cooling. From the simulations, we synthesize spatially and spectrally
resolved focal-plane data as they would be collected with XMM-Newton/EPIC, an
X-ray instrument commonly used in these studies.
  We devise and tune up two diagnostic tools, the first based on the
mean-photon energy vs. count rate scatter plot and the second on the spectral
analysis of the interaction region, that can be used to highlight the effects
of thermal conduction and to derive the shock speed in case of efficient
conduction at work. These tools can be used to ascertain information from X-ray
observations, without the need to develop detailed and ad-hoc numerical models
for the interpretation of the data.
