Total Accessibility Matrix (T)The total accessibility matrix (T) is obtained from the following
procedure:

Construct the connectivity matrix (C1). It is a
matrix where for each cell a value of 1 or 0 is used to denote
in a connection exists between two node pairs. On the above
network node C is having the highest degree, which is the sum of
all the connections this node has (4).

Construct the second order (two-linkages paths) connectivity
matrix (C2). The total number of two-linkages paths (matrix
C2) equals to C1*C1. Each cell in the C2 matrix is the result of
the summation of the product of each corresponding row and column
in the C1 matrix. For instance, cell A-B in matrix C2 (see above)
is constructed from the following: 0*1 + 1*0 + 1*1 + 1*0 + 0*0.
It indicates that there is only one possible two-paths link between
node A and node B (A-C-B). C2 matrix indicates
that there are two possible two-linkages paths between C and A (C-B-A
and C-D-A).

Repeat the construction of the Nth order connectivity matrices
until the number of Nth-linkages paths is equivalent to the diameter
(path between most distant nodes) of the network. A 3rd order connectivity
matrix (C3) would be equal to C1*C2. A network that has a diameter
of 4 would require the construction of 4 matrices (C1 to C4). Since
the above network has a diameter of 2, only two matrices, C1 (1st
order connectivity) and C2 (2nd order connectivity), need to be
constructed.

Construct the total accessibility matrix (T). For the
above network, matrix C2 (two-linkages paths) is added to matrix
C1 (single paths; connectivity matrix). This summation represents
for each node the total number of paths. For this network, there
are thus 46 possible paths, with node C having the largest number
(12); either originating from it or having it as a destination.