  In the context of class S theories and 4D/2D duality relations there, we
discuss the skein relations of general topological defects on the 2D side which
are expected to be counterparts of composite surface-line operators in 4D class
S theory. Such defects are geometrically interpreted as networks in a three
dimensional space. We also propose a conjectural computational procedure for
such defects in two dimensional SU(N) topological q-deformed Yang-Mills theory
by interpreting it as a statistical mechanical system associated with ideal
triangulations.
