“…In previous approaches based on G-SEQ (Artigues, Billaut, & Esswein, 2005;Artigues, Jean-Charles, Cheref, Mebarki, & Yahouni, 2016;Billaut & Roubellat, 1996;Cheref, Artigues, & Billaut, 2016a, 2016bErschler & Roubellat, 1989), a G-SEQ is a valid solution iff any J-SEQ constructed by ordering the tasks within a group is valid in the sense of Definition 1. For the single machine problem, that means that a G-SEQ is valid iff for any pair (i, j) ∈ E, the group of job i is ordered strictly before the group of job j in the G-SEQ.…”