  In this note we show that if a boundary system in the sense of (Schubert et
al. 2015) gives rise to any skew-self-adjoint extension, then it induces a
boundary triplet and the classification of all extensions given by (Schubert et
al. 2015) coincides with the skew-symmetric version of the classical
characterization due to (Gorbachuk et al. 1991). On the other hand we show that
for every skew-symmetric operator there is a natural boundary system which
leads to an explicit description of at least one maximal dissipative extension.
This is in particular also valid in the case that no boundary triplet exists
for this operator.
