}Definition [Free-Choice]:
}N is called free-choice iff all p in S such that
|p•|>1,
•(p•) = p
}
}
}
}Definition [Asymmetric-Choice]:
}N is called asymmetric-choice (or simple net) iff for
every two
places p1, p2, p1•∩ p2• ≠ Ø è p1• ≤ p2• or p1• ≥ p2•
}