Algorithm 2 GetPFS (OD, DD, FS, old, new)
Input: OD, DD, FS, old, new
Output: PFS
1:	Put FS into PFS
2:	Set $s1=PrefixSpan+\left(\left\{\right\},old+new,min\_sup\times \left|new\right|\right)$
3:	Put$s1$into PFS
4:	For$b$in PFS
5:	Construct projection database $S$ of DD to the part of $b$ that belongs to OD
6:	Set $s2=PostfixSpan+\left(b,S,min\_sup\times \left|new\right|\right)$
7:	Put $s2$ into PFS