BOM-based Planning
BOM-based planning describes a structural principle of engineering execution:
execution readiness follows product structure, not schedules alone.
In engineering-driven projects, what ultimately becomes executable is defined by the structure of the product.
The Bill of Materials (BOM) therefore provides the primary reference for understanding execution behaviour.
Product structure as execution reference
The BOM represents the decomposition of a product into assemblies, sub-assemblies, and components.
From an execution perspective, this structure defines:
- what must become executable,
- how dependencies propagate,
- and where execution constraints accumulate.
Planning that ignores product structure cannot reliably reflect execution reality.
In this context, BOM refers to product structure as an execution reference, not merely a procurement or documentation artefact.
Why schedule-centric planning is insufficient
Schedule-centric planning abstracts execution away from product structure.
As a result:
- dependencies are linearised artificially,
- readiness is assumed at fixed dates,
- and execution risk remains hidden until plans fail.
Schedules describe when activities are intended to occur.
They do not describe whether the product is structurally executable at a given point in time.
Dates describe intention.
Product structure determines executability.
Execution readiness follows structure
Execution readiness emerges when elements of the product structure reach a sufficient state of definition and dependency resolution.
This readiness:
- cannot be assigned directly to tasks,
- cannot be derived from schedule progress,
- and cannot be inferred reliably from isolated indicators.
It must be observed structurally, through the state of assemblies and their components.
Propagation of dependencies
Dependencies in engineering execution propagate along product structure.
Changes, unresolved interfaces, or missing definition at one level of the BOM affect executability downstream.
BOM-based planning makes these propagation paths visible by:
- anchoring execution to structure,
- exposing where readiness is blocked,
- and revealing how local changes affect global execution.
Relation to assembly-driven execution
BOM-based planning builds directly on assembly-driven execution.
While assemblies act as execution carriers, the BOM defines:
- their internal composition,
- their structural dependencies,
- and the conditions under which they become executable.
Together, these principles describe how execution readiness accumulates structurally.
Relation to Product Flow
Product Flow applies the principle of BOM-based planning by linking execution visibility directly to product structure.
The system uses BOM relationships to:
- observe readiness across assemblies,
- analyse dependency propagation,
- and expose structural execution risk.
BOM-based planning is therefore a core execution principle underlying Product Flow as an Engineering Execution System.
Relation to other execution principles
BOM-based planning connects multiple execution principles:
- It refines assembly-driven execution at structural level.
- It enables phase-based engineering execution by defining readiness transitions.
- It supports visibility and risk by revealing structural bottlenecks.