  Requirements are investigated in this paper for each descriptor form
subsystem, with which a causal/impulse free networked dynamic system (NDS) can
be constructed. For this purpose, a matrix rank based necessary and sufficient
condition is at first derived for the causality/impulse freeness of an NDS, in
which the associated matrix depends affinely on subsystem connections. From
this result, a necessary and sufficient condition is derived for each
subsystem, such that there exists a subsystem connection matrix that leads to a
causal/impulse free NDS. This condition further leads to a necessary and
sufficient condition for the existence of a local static output feedback that
guarantees the construction of a causal/impulse free NDS. A prominent property
of these conditions are that all the involved numerical computations are
performed independently on each individual subsystem, which is quite attractive
in reducing computation costs and improving numerical stability for large scale
NDS analysis and synthesis. Situations have also been clarified in which NDS
causality/impulse freeness is independent of subsystem connections. It has also
been made clear that under some situations, local static output feedbacks are
not helpful in constructing a causal NDS.
