Algorithm 2. Word Concretization Function γ(w).

Input: a word w

Output: a set matrix_set of arrays

1: rnum = iRow/oRow, cnum = iCol/oCol

2: if w.length ≠ rnum × cnum then

3:  return null

4: end if

5: for wi = 0, . . . ,w.length − 1 do

6:  data[wi] = γsS (word[wi])

7: end for

8: S = {m | m[ri : ri + oRow][ci : ci + oCol] ∈ data[ri × cnum + ci]}

9: matrix_set = {in | in ∈ γv(m) and m ∈ S}

10: return matrix_set