Stock
Stock is how inventory levels are represented. Multiple stock items can exist for a given part, and each stock item is assigned a location.
Stock has a location
Every instance of 'stock' is assigned to a location.
See Locations for more details on the concepts behind locations.
Stock changes are a ledger
It's not good enough to only track the current quantity of a part, so we track every change to the stock level and metadata about when, why and how the stock change occured.
Stock changes to quantity split the stock
When partial quantity is taken from a stock location and moved to another location, the stock is split in two.
Stock with the same location and unit of measure coalesce
If stock is moved from into a location that already has stock of the same part with the same unit of measure, they will be combined into a single stock item. This
Stock changes can transmute one part into another
A stock change can link the act of one part being transformed into another part and the resulting change in quantity for both parts.
Consider a manufacturing process turning a block of steel into a bracket.