[SRILM User List] how null nodes are created?

[yasser hifny]

Hi,
I have this LM and its pfsg is attached as a pdf. Can you please detail how the null nodes are created?
\data\ngram 1=6ngram 2=7ngram 3=1
\1-grams:-0.5228788 </s>-99 <s> -0.7781513-0.69897 cat -0.30103-1 dog -0.30103-1 set -0.30103-0.5228788 the -0.4771213
\2-grams:-0.05387538 <s> the -0.1439066-0.39794 cat </s>-0.5228788 cat set-0.1870866 dog </s>-0.1870866 set </s>-0.2466723 the cat-0.69897 the dog
\3-grams:-0.1618508 <s> the cat
\end\
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