# Operand-Free Outcome Surface

> A rule or precondition that a surface carrying one jointly authored product declares that one writer per record has no operand there, and settles a collision by announcement and by each author cutting its own duplicate.

Record: `architecture:operand-free-outcome-surface`
Kind: constraint
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: mandatory
Scope: surface, authorship
Canonical: https://banes-lab.com/ontology#architecture-operand-free-outcome-surface

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Write Barrier](https://banes-lab.com/records/architecture/write-barrier.md) and before [Projection Channel](https://banes-lab.com/records/architecture/projection-channel.md).

## Repair

- Refactored by: Declare the Missing Operand, Settle Collisions by Announcement
- Detected by: an outcome surface with no declaration that the invariant has no operand there
- Violated by: assuming the one-writer invariant covers a jointly authored surface, or fencing such a surface into per-party spans
- Measured by: outcome surfaces missing the declaration
- Enforced by: coordination review

## Requires

- [Outcome Surface](https://banes-lab.com/records/lexicon/outcome-surface.md)

## Reinforces

- [Stated Invariant](https://banes-lab.com/records/architecture/stated-invariant.md)

## Enables

- [Traceable Guarantee](https://banes-lab.com/records/lexicon/traceable-guarantee.md)

## Conflicts with

- [Contradicted Invariant](https://banes-lab.com/records/architecture/contradicted-invariant.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)

## 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)