When assigning jobs (or tasks or projects) to a starting time, with a ready and due time for each job, there are different scenarios:

  • A) Front loading: Assign all jobs as soon as possible. As close as possible to their ready time. For example, we need build 5 red cars before the end of year, so we could them now in October or wait until November or December. With Front loading, we'll build them now in October, unless there's a more urgent order (for example to build blue cars this month), which would push them out to November.
  • B) Assign all jobs on their ideal execution time. For example, we need to clean a house once every 7 days. We cleaned it yesterday. We could clean it again today, but that will just mean we have to clean it sooner next week. Ideally, we wait 6 days (no more, no less) to clean it. But it's fine if there's sometimes a few more or less days between the cleaning, due to other more priority jobs.
  • C) Back loading?: Assign all jobs as late as possible. As close as possible to their due time.

What the canonical terminology for B) and C)?


1 Answer 1


In the scheduling literature, there are some concepts to define a sequence/schedule plan. Optimal, non-delay, active, and semi-active schedule. W.r.t this and how you would change a sequence into a schedule, also, there are some rules so-called dispatching rules.

Indeed, what you are looking for sounds like, forward scheduling, JIT scheduling, and backward scheduling respectively.

For more details: Scheduling: Theory, Algorithms, and system by Pinedo, Michael L.

  • $\begingroup$ Interesting, "front loading" (from timetabling literature, for example for exam scheduling) and "forward scheduling" (from scheduling literature) are clearly the same thing indeed. $\endgroup$ Commented Oct 22, 2021 at 13:13
  • $\begingroup$ The second one isn't really JIT scheduling, I'd argue though. If you want to clean your house every 7 days, making the next sunday the ideal date, then cleaning it a day late doesn't make it over time (it's still in time, just not ideal). $\endgroup$ Commented Oct 22, 2021 at 13:17
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    $\begingroup$ @GeoffreyDeSmet My understanding is that JIT is based on a due date (or, for sequences of tasks, the final due date backtracked by the processing times of the remaining steps). If you are going to allow housekeeping to be approximately once a week (maybe less), I'm not sure you have a firm enough due date to call the wait six (or so) days JIT. At least as originally envisioned, JIT would require more precision than that. $\endgroup$
    – prubin
    Commented Oct 22, 2021 at 15:25
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    $\begingroup$ @Geoffrey, I am happy that the answer would be useful. As the result of the schedule plan heavily depends on how the objective function would be determined the difference between the objective functions comes from that. Suppose, in some cases, earliness wouldn't be allowed, in the other cases tardiness/lateness wouldn't be allowed, and in another, neither earliness nor tardiness will not be accepted. These situations referred to forward, backward, and JIT scheduling respectively. $\endgroup$
    – A.Omidi
    Commented Oct 22, 2021 at 15:59
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    $\begingroup$ In the literature, the term "due date" is used when it is soft. Otherwise, the term "deadline" is used. Some problems have jobs with both due dates and deadlines. For example doi.org/10.1016/j.cie.2019.106102 $\endgroup$
    – fontanf
    Commented Oct 26, 2021 at 9:51

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