# Write Scope and Read Population

> A design rule that a run declares the paths it writes and publishes the set it read as two declarations, because collision is decided by the first and a published result's validity by the second.

Record: `architecture:write-scope-and-read-population`
Kind: principle
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: mandatory
Scope: run, invocation
Canonical: https://banes-lab.com/ontology#architecture-write-scope-and-read-population

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Section Lifetime Divergence](https://banes-lab.com/records/architecture/section-lifetime-divergence.md) and before [Read-Time Join](https://banes-lab.com/records/architecture/read-time-join.md).

## Repair

- Refactored by: Declare the Write Scope, Publish the Read Population
- Detected by: a run that reads more than it writes and publishes only its write scope
- Violated by: declaring one scope and using it both to detect collisions and to decide whether a result answers a later question
- Measured by: runs publishing no read population
- Enforced by: the coordination writer check, which fails a writer a run reaches outside the sanctioned set

## Requires

- [Write Scope](https://banes-lab.com/records/lexicon/write-scope.md)
- [Read Population](https://banes-lab.com/records/lexicon/read-population.md)

## Reinforces

- [Determinism](https://banes-lab.com/records/architecture/determinism.md)

## Enables

- [Shared Invocation](https://banes-lab.com/records/lexicon/shared-invocation.md)

## Severity

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

## Category

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

## Reinforced by

- [Read-Time Join](https://banes-lab.com/records/architecture/read-time-join.md)

## Linked from

- [Correctness / Determinism / Verification](https://banes-lab.com/ontology/principles/architecture-category-correctness-determinism-verification.md)
- [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

- [unsanctionedWriters](https://banes-lab.com/source/coordination/tools/core/validators/writer.validator.ts.md)
- [models/invocation.model.md](https://banes-lab.com/source/coordination/models/invocation.model.md.md)