java – 无法理解CYK算法的伪代码

let the input be a string S consisting of n characters: a1 ... an.
let the grammar contain r nonterminal symbols R1 ... Rr.
This grammar contains the subset Rs which is the set of start symbols.
let P[n,n,r] be an array of booleans. Initialize all elements of P to false.
for each i = 1 to n
  for each unit production Rj -> ai
    set P[i,1,j] = true
for each i = 2 to n -- Length of span
  for each j = 1 to n-i+1 -- Start of span
    for each k = 1 to i-1 -- Partition of span
      for each production RA -> RB RC
        if P[j,k,B] and P[j+k,i-k,C] then set P[j,i,A] = true
if any of P[1,x] is true (x is iterated over the set s,where s are all the indices for Rs) then
  S is member of language
else
  S is not member of language

这些部分让我很困惑：

for each production RA -> RB RC
      if P[j,A] = true

有人会给出一些关于这些伪代码的提示吗？