  We study consequences of stationary and semi-stationary set reflection. We
show that the semi stationary reflection principle implies the Singular
Cardinal Hypothesis, the failure of weak square principle, etc. We also
consider two cardinal tree properties introduced recently by Weiss and prove
that they follow from stationary and semi stationary set reflection augmented
with a weak form of Martin's Axiom. We also show that there are some
differences between the two reflection principles which suggest that stationary
set reflection is analogous to supercompactness whereas semi-stationary set
reflection is analogous to strong compactness.
