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When you submit a BOM import, Variable performs several operations to create your product structure. This guide explains what happens behind the scenes.

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Import processing overview

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What gets created

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Level 0: Root products

Rows with bomLevel: 0 or no parent reference become root Products. These are your company’s own products that you manufacture or assemble. 
bomLevel,productSku,productName
0,BIKE-001,Mountain Bike
Creates a Product:
  • Type: LIVE (or UNKNOWN if incomplete)
  • Owned by your company
  • Ready to receive inputs from child rows
If a product with the same SKU already exists, Variable reuses it instead of creating a duplicate.

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Level 1+: Supplier parts and materials

Child rows create a chain of related items. Variable uses a 3-level structure to accurately model your supply chain:
LevelWhat it representsExample
ProductYour finished good or assemblyMountain Bike
Supplier PartSpecific part from a specific supplier”Alloy Rim from RimSupply”
MaterialGeneric material typeAluminum Alloy 6061
DatasetEmission factors from databaseecoinvent: Aluminum production

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The 3-level BOM structure explained

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Why three levels?

Consider this scenario: you buy an “Alloy Rim” from “RimSupply”. That part is made of aluminum. To calculate its carbon footprint, you need to:
  1. Know the part (Alloy Rim) and quantity you’re using
  2. Know the supplier (RimSupply) to track your supply chain
  3. Know the material (aluminum) to assign the correct impact data
Variable maintains all three pieces of information.

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How supplier parts work

When you import a BOM row with supplier information: 
productSku,supplierName,supplierPartId,materialName,quantity,unitCode
RIM-001,RimSupply,RS-RIM-42,Aluminum Alloy,0.3,kg
Variable creates:
  1. Supplier Part - A Material node representing “RS-RIM-42 from RimSupply”
    • Linked to the supplier company
    • Stores the supplier’s part number
  2. Material - A Material node representing “Aluminum Alloy”
    • Generic material type
    • Where you’ll assign the dataset
  3. Input relationships
    • Your Product uses the Supplier Part (quantity from BOM)
    • The Supplier Part contains the Material (weight from BOM)

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Weight assignment rules

How Variable assigns weights depends on the chain depth:

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3-level chain (Part to Supplier Part to Material)

When the supplier part has an associated material:
  • Supplier Part gets quantity from BOM (e.g., 1 piece)
  • Material gets weight from BOM (e.g., 0.3 kg)
productSku,supplierPartId,materialName,quantity,weightAmount,weightUnitCode
PEDAL-001,SUP-PEDAL-1,Aluminum Alloy,2,0.15,kg
Result: The product uses 2 pedals, each pedal contains 0.15 kg of aluminum.

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2-level chain (Part to Supplier Part only)

When there’s no separate material:
  • Supplier Part gets both the quantity and the weight unit
  • The supplier part IS the material input
productSku,supplierPartId,quantity,weightAmount,weightUnitCode
FRAME-COAT-001,SUP-COAT-1,1,0.8,kg
Result: The product uses 0.8 kg of frame coating (the supplier part itself is the material input).
Variable detects the chain depth automatically by checking if any row for a given supplier part also has a materialId or materialName.

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Supplier relationships

When you include supplier columns:
ColumnWhat happens
supplierNameCreates or matches a Company node
supplierIdUses your internal ID for matching
supplierPartIdStored on the supplier part for reference
Supplier matching:
  • First tries to match by supplierId
  • Then by supplierName
  • Creates a new supplier if no match found

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Idempotency: safe re-imports

BOM imports are designed to be re-run safely:

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Product deduplication

  • Products matched by SKU within your company
  • Existing products are reused, not recreated - and not updated either. Variable leaves existing matches alone; it won’t overwrite their name, supplier, or other fields with newer values from your file.

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Input deduplication

New inputs are only added when:
  • The product was created during this import, OR
  • The product has type UNKNOWN, OR
  • The product has no existing inputs
Products that are already LIVE with inputs are considered “fully modeled” and won’t receive additional inputs from a re-import.
If you need to add inputs to an existing LIVE product, you can either change it to UNKNOWN first, or add inputs manually through the UI.

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Duplicate detection

Within the same import, duplicate inputs are detected by comparing:
  • Source product ID
  • Quantity
  • Unit code

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After import completes

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Automatic calculations

Variable automatically triggers CO2e recalculation for all affected products. This cascades through your product hierarchy.

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What you need to do next

Materials are created but not yet linked to datasets. Assign a dataset to each one in the app to complete your footprint calculations. After a BOM import, these relationships exist in Variable:

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Next steps