Inventory and master item models
The master item model defines an item’s identity, units of measure, variants and tracking rules. Every inventory screen inherits its limits.
Much of the stock confusion on a shop floor traces back to an item that was set up ambiguously.
Key facts
- Tracking (none, lot or serial) is set on the item and decides whether traceability is possible.
- A quantity should always appear with its unit.
- Variants as one item with attributes keep the catalogue small and complicate stock views.
- Changing the tracking rule after stock exists leaves older balances without a lot.
- A strict item model prevents bad data and slows down product introductions.
What it covers
| Decision | What depends on it |
|---|---|
| Tracking: none, lot or serial | Whether traceability is possible |
| Base unit and conversions | Every quantity entered or displayed |
| Variants or separate items | Planning, pricing and stock views |
| Stocked, non-stocked or service | Whether receipts create inventory |
| Shelf life | Expiry, FEFO picking, quarantine |
The item record sits upstream of receiving, inventory, picking, costing and labels. A decision made on the item shows up in all of them.
Who uses it
| Role | What they do with the item model |
|---|---|
| Engineering or product team | Introduce new items and their variants |
| Purchasing | Buy in supplier units |
| Warehouse and production | Receive, store and consume in stock units |
| Sales | Sell in sales units |
| Accounting | Value stock at item level |
What makes it hard to design
Units of measure. A material may be received in containers and consumed in a volume unit. Redbrix designs entry screens to distinguish container count, contents and unit conversions. Redbrix shows the applicable conversion at entry; variable contents require a recorded quantity rather than an assumed fixed ratio.
Variants. One item per size or grade multiplies records. One item with attributes keeps the catalogue small and complicates stock views. The deciding factor is whether variants are planned and costed separately.
Decisions that need several departments. Tracking, units and shelf life are often decided by people who do not create the item record. The setup screen has to make those fields hard to skip and easy to understand for whoever fills them in.
Balances received before a tracking change have no lot, and the screen should state this instead of showing an empty lot field.
Trade-offs
- A strict item model prevents bad data. It also slows down product introductions, because each new item needs decisions that sales or engineering cannot make alone.
- One item with attributes keeps the catalogue small. Separate items keep stock views simple.
Common mistakes
- Changing the tracking rule after stock exists, with no indication on screen that older balances have no lot
- Quantities shown without their unit
- Conversions hidden from the person entering a quantity
- Variants modelled as attributes when they are planned and costed separately
Where Redbrix has worked on this