# Section Lifetime Divergence

> A rule or precondition that a file states a default lifetime and each section declares only the axes on which it differs, since the narrower unit is the more constrained one.

Record: `architecture:section-lifetime-divergence`
Kind: constraint
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: recommended
Scope: surface, section
Canonical: https://banes-lab.com/ontology#architecture-section-lifetime-divergence

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Independent Lifetime Axes](https://banes-lab.com/records/architecture/independent-lifetime-axes.md) and before [Write Scope and Read Population](https://banes-lab.com/records/architecture/write-scope-and-read-population.md).

## Repair

- Refactored by: Declare the File Default, Declare Each Divergent Section
- Detected by: an operation permitted by the file's lifetime acting on a section whose own lifetime forbids it
- Violated by: stating one lifetime for a file whose sections live differently, so the file's word authorizes operations on the part that forbids them
- Measured by: divergent sections carrying no declaration
- Enforced by: coordination review

## Requires

- [Retention](https://banes-lab.com/records/lexicon/retention.md)
- [Mutability](https://banes-lab.com/records/lexicon/mutability.md)

## Reinforces

- [Independent Lifetime Axes](https://banes-lab.com/records/architecture/independent-lifetime-axes.md)

## Enables

- [Governed Removal](https://banes-lab.com/records/lexicon/governed-removal.md)

## Severity

- [recommended](https://banes-lab.com/records/vocabulary/severity-recommended.md)

## Category

- [Coordination Surfaces](https://banes-lab.com/records/architecture-category/coordination-surfaces.md)

## Linked from

- [Coordination Surfaces](https://banes-lab.com/ontology/principles/architecture-category-coordination-surfaces.md)
- [Coordination Surfaces](https://banes-lab.com/ontology/lexicon/lexicon-category-coordination-surfaces.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)

## Evidence in the code

- [models/coordination.model.md](https://banes-lab.com/source/coordination/models/coordination.model.md.md)