OPS.10.2:4.2 - Construct precedence, occupation and calendar conditions

A precedence relation states which event must occur before another operation may begin. For a continuous operation i of duration p_i, finish f_i equals start s_i plus p_i. A finish-to-start relation from i to j with required delay l requires s_j >= f_i + l. At a join, every required predecessor must satisfy its relation. An actual partial handover can use an earlier event, provided the downstream work can use that partial result.

Resource sharing adds a different condition. Two operations requiring the same exclusive resource cannot occupy it at the same time. Their order is a choice unless the operation already fixes it. For a pool, check how many eligible members are needed simultaneously; one free but unqualified person does not supply the required capability.

Recover each occupation separately. A machine may hold an order for three hours while its operator is needed only in the first hour. Represent the machine interval and that operator interval with their common start. Apply each resource’s capacity and calendar to its own intervals. Use half-open intervals, including the start and excluding the finish, when a resource can pass immediately to the next operation.

Distinguish three calendar conditions that require different placements:

• A continuous occupation must fit wholly inside an available window.
• Work that may pause can accumulate processing across open windows, with any restart cost included.
• A machine may continue through an operator’s absence when that phase needs no attendance.

A rule allowing an operation to start during working hours does not establish that its later occupied hours are available. Where several resources are needed together, find a window in which their required occupations are jointly possible.

Check that the precedence relations can be satisfied. A finish-to-start cycle with positive total required duration and delay is an obstruction. When the work actually revisits a station, represent the later visit as a later operation rather than requiring one operation to precede itself.

MMP.10 supplies the joint formulation. Keep the operational reason for a condition recoverable: actual precedence, chosen resource order, calendar closure, admission policy or deadline. A chosen order can be reconsidered without pretending the technological route changed.