# Derived Party Count

> A design rule that the number of parties a body of work implies is derived from how the work is partitioned into concerns, so two parties holding one partition reach one count.

Record: `architecture:derived-party-count`
Kind: principle
Layer: [Execution Core](https://banes-lab.com/records/layer/execution-core.md)
Severity: contextual
Scope: allocation, coordination
Canonical: https://banes-lab.com/ontology#architecture-derived-party-count

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Period-Decided Disposition](https://banes-lab.com/records/architecture/period-decided-disposition.md) and before [Fan-In Ceiling](https://banes-lab.com/records/architecture/fan-in-ceiling.md).

## Repair

- Refactored by: Derive the Partition, Count Its Concerns
- Detected by: a count that moved while no partition moved
- Violated by: choosing a party count as a preference and allocating work to fit it
- Measured by: counts proposed with no partition behind them
- Enforced by: none: no mechanism derives the partition, so the count rests on review

## Requires

- [Concern Partition](https://banes-lab.com/records/lexicon/concern-partition.md)

## Reinforces

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

## Enables

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

## Severity

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

## Category

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

## Reinforced by

- [Fan-In Ceiling](https://banes-lab.com/records/architecture/fan-in-ceiling.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

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