OPM on the other hand caters to capabilities to allow for multiple units of measure because the flexibility in batch production is required in process industries. e.g Chemical Industries, food processing etc. This involves complex internal processes and need a high level of control.
Eg: You mix x kgs of sugar and n litres of milk, you get a sweet as the output. This can be in kilos, litres or smaller units. If you do not allow the water to evaporate the output will be a liquid, if you heat longer the output will be a burfi.
What is the difference between the two?
1)ODM uses BOM (Bill of Materials), OPM uses formulas and Recipes
2)UOM will vary depending on the material used in OPM but in ODM UOM will be each or unit
3)ODM assembles or builds things, OPM mixes , blends and transforms or converts.
4)OPM is driven by item attributes and ODM is driven by part number