OPS.15.1:4.3 - Construct the intervals and count changes

For each relevant subject or visit, pair the boundary events belonging to that episode. Its elapsed residence is end time minus start time. If only a range for an endpoint is known, propagate that range instead of selecting an unsupported point.

For resource use, reconstruct the intervals during which the resource is occupied under the chosen meaning. Occupied machine time, operator attention and reservation can differ. A machine can run unattended while its operator serves another machine.

Combine intervals according to the quantity. For a single resource’s occupied fraction, take the duration of the union of its occupied intervals; overlapping descriptions of the same occupation are counted once. To measure total occupied resource-hours across distinct resources, sum those resource-specific durations. To measure part residence during batch processing, retain each part’s interval.

Calendar time and available working time are also different quantities. For working time, intersect the interval with the relevant open-calendar intervals before adding durations. A calendar conversion does not remove a customer’s overnight wait from elapsed service time.

For counts, follow entries and exits of the chosen population. With fixed case identity and no splitting or merging, ending population equals starting population plus entries minus exits. Include cancellations or other exits under their own meanings. If the subject is split or combined, recover the changed counting unit before using that balance.