A job leaving through a reject path still leaves the counted system. A balance based only on accepted output can misstate the remaining inventory.
List all counted entries and exits
Flowchart accounting can compare counts at entry and exit points, including multiple sources and sinks. For a population that is neither created nor combined internally, ending inventory equals starting inventory plus entries minus all exits. Accepted output is only one exit category when the model also removes scrap or canceled jobs. Primary reference: AnyLogic counting agents across multiple entry and exit points.
On an original boundary sketch, draw each path that crosses outward and name its category. If an internal operation splits or combines entities, simple job-count conservation may require another counting unit. Do not apply an unchanged-item ledger after silently changing what one entity represents.
Reconcile a fictional balance
Suppose a hypothetical system starts with 5 items, admits 20, sends 18 through an accepted exit and 2 through a scrap exit. Ending inventory is 5 + 20 − 18 − 2 = 5 items. Subtracting accepted output alone would report 7 and wrongly retain the two scrapped items.
This is an inventory identity, not an acceptable scrap allowance or a quality-yield estimate. The example counts unchanged items crossing a specified boundary. A returned item that remains within that boundary is not an exit unless the chosen model defines it as one.
Review identities and endpoint state
Prepare a trial reconciliation listing starting IDs, newly admitted IDs, each exit category and IDs still inside. Compare the count balance with the endpoint state, then investigate any duplicate departure or unrecorded creation. Keep accepted and scrap columns separate while including both in the total outflow.
For an actual analysis, use the authorized disposition definitions and data rather than these fictional numbers. The guide does not certify batch reconciliation or a pharmaceutical release record. Its purpose is to expose an omitted outflow in a modeled inventory calculation.
Customer Questions
Does scrap leaving the boundary count as outflow?
Yes, under an unchanged-item population definition.
What is ending inventory in the example?
Five items after both accepted and scrap exits are counted.
Can an unchanged-item balance handle entity merging automatically?
No. The counting unit and internal transformations need explicit treatment.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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