# ifc-material layer instructions
Scope: material-layer identity and composition. Follow the crate `../../AGENTS.md`.
## Owns
- layer identity, material link, name, description, category, and priority
- authored layer thickness and ordered layer-set membership
- authored usage direction, sense, offset, extent, and offset-layer values
## Does not own
- geometric interpretation of directions or offsets
- offset transforms, wall solid generation, or quantity computation
`ifc-geometry::input::material_usage` may project the same raw IFC record to
remain domain-independent, but it owns lowering rather than material semantics.
## Growth map
`definition.rs`, `set.rs`, and `usage.rs` are the implementation owners. Extend
them with focused tests; do not add parallel modules.