  Various topics concerning the entanglement of composite quantum systems are
considered with particular emphasis concerning the strict relations of such a
problem with the one of attributing objective properties to the constituents.
Most of the paper deals with composite systems in pure states. After a detailed
discussion and a precise formal analysis of the case of systems of
distinguishable particles, the problems of entanglement and the one of the
properties of subsystems of systems of identical particles are thourougly
discussed. This part is the most interesting and new and it focuses various
subtle questions which have never been adequately discussed in the literature.
Some inappropriate assertions which appeared in recent papers are analyzed. The
relations of the main subject of the paper with the nonlocal aspects of quantum
mechanics, as well as with the possibility of deriving Bell's inequality are
also considered.
