st=>start: Start|past:>http://www.baidu.com
e=>end: End:>http://www.baidu.com
op1=>operation: My Operation|past
op2=>operation: Stuff|current
sub1=>subroutine: My Subroutine|invalid
cond=>condition: Yes or No?|approved:>http://www.baidu.com
c2=>condition: Good idea|rejected
io=>inputoutput: catch something...|request

st->op1(right)->cond
cond(yes, right)->c2
cond(no)->sub1(left)->op1
c2(yes)->io->e
c2(no)->op2->e