  Decomposition of any Boolean Function BF_n of n binary inputs into an optimal
inverter coupled network of Symmetric Boolean functions SF_k (k \leq n) is
described. Each SF component is implemented by Threshold Logic Cells, forming a
complete and compact T-Cell Library. Optimal phase assignment of input
polarities maximizes local symmetries. The "rank spectrum" is a new BF_n
description independent of input ordering, obtained by mapping its minterms
onto an othogonal n \times n grid of (transistor-) switched conductive paths,
minimizing crossings in the silicon plane. Using this ortho-grid structure for
the layout of SF_k cells, without mapping to T-cells, yields better area
efficiency, exploiting the maximal logic path sharing in SF's. Results obtained
with an optimization tool "Ortolog" based on these concepts, for very fast
O(n^2) detecting and enhancing local symmetries of a BF_n, are reported.
Relaxing symmetric- to planar- Boolean functions is sketched, to improve low-
symmetry BF decomposition.
