Product Structure

A product structure is the hierarchical decomposition of a product into its constituent components and subassemblies, represented as a tree or network from which bills of materials are derived. In variant management, the product structure is the foundation on which variant documentation, configuration management, and production planning are built — it determines how variants are represented, where variation is encoded, and how individual variant BOMs are derived.

The product structure is sometimes called the BOM structure or engineering BOM structure. It describes not just the parts list for a specific product, but the parent-child relationships between assemblies, subassemblies, and components that define how the product is built.

Levels of a product structure

A typical product structure is organized in levels from top to bottom:

• Level 0 — End product — The complete, deliverable product as sold to the customer.
• Level 1 — Major assemblies — The main subassemblies into which the product is divided (e.g., chassis, powertrain, body).
• Level 2+ — Subassemblies and components — Progressive decomposition down to individual purchased parts or raw materials.

The number of levels varies by product complexity. A simple industrial device may have three levels; a commercial aircraft may have fifteen or more.

Product structure and variant management

In a product family with multiple variants, the product structure must represent all variants — not just one. There are two principal approaches:

Separate structures per variant — Each product variant is represented as an independent product structure. This is simple to implement but scales poorly: with dozens or hundreds of variants, maintaining parallel structures is labor-intensive, and shared changes must be propagated manually to every variant’s structure.

Shared structure with variant logic — A single product structure represents the entire product family, with variation encoded at the nodes where alternatives exist. The 150% BOM 150% BOM (ˌwən-ˌfif-tē pər-ˈsent ˌbil əv mə-ˈtir-ē-əlz) n. A 150% BOM lists all possible components across all product variants, serving as the master structure for subtractive configuration in variant management. is the classic example of this approach: a single structure lists all possible components across all variants; individual variant BOMs are derived by applying variant rules or configuration selections.

The shared-structure approach is the basis of all systematic variant management. It requires explicit modeling of variation points Variation Point (ˌver-ē-ˈā-shən ˈpȯint) n. A variation point is a specific location in a product or system architecture where a decision between alternatives must be made to create a specific variant. within the structure and constraint rules that determine which components apply to which variants.

Product structure in PLM systems

In Product Lifecycle Management (PLM) systems, the product structure is the central data object. PLM systems manage:

• Which components belong to which assembly at which level
• Effectivity dates and engineering change states for each component
• Variant rules or configuration rules that select components based on product configuration
• Document links (drawings, specifications) attached to each node

In ERP systems such as SAP, the product structure is represented as a BOM (Bill of Materials) — typically an engineering BOM in the PLM system and a manufacturing BOM in the ERP system, which may differ in structure and level of detail.

Configuration and the product structure

When a customer selects a specific product configuration, the configuration rules are applied to the product structure to derive the specific BOM for that variant. This derivation process — from the complete product structure to a specific variant BOM — is the core operation of a variant management system:

1. The customer selects options (e.g., engine type, color, optional packages).
2. The configuration rules resolve which components in the product structure are applicable to those selections.
3. The resulting set of applicable components forms the 100% BOM for that specific variant.
4. This 100% BOM is transferred to the ERP system for production planning and procurement.

Examples

• Hydraulic cylinders — A manufacturer offers cylinders in multiple bore sizes, stroke lengths, seal materials, and mounting variants. A shared product structure represents all combinations; variant rules select the appropriate piston, cylinder tube, seal kit, and mounting hardware for each configured order.
• Modular office furniture — A furniture line uses a shared product structure for a desk family, with variation at the leg assembly, desktop surface, drawer unit, and cable management system nodes. The structure supports hundreds of valid desk configurations from a managed set of components.

Frequently asked questions