# Places and Transitions

> The requirement that a modeled system be expressed as places holding tokens and transitions that move them.

Record: `lexicon:places-and-transitions`
Kind: constraint
Layer: [Atomic Boundary](https://banes-lab.com/records/layer/atomic-boundary.md)
Canonical: https://banes-lab.com/ontology/lexicon#lexicon-places-and-transitions

Listed in [Lexicon terms](https://banes-lab.com/api/records/lexicon.md), after [Modeling Overhead](https://banes-lab.com/records/lexicon/modeling-overhead.md) and before [Reachability and Deadlock Analysis](https://banes-lab.com/records/lexicon/reachability-and-deadlock-analysis.md).

## Category

- [Transactions / State / Concurrency](https://banes-lab.com/records/lexicon-category/transactions-state-concurrency.md)

## Required by

- [Petri Nets](https://banes-lab.com/records/architecture/petri-nets.md)

## Linked from

- [Transactions / State / Concurrency](https://banes-lab.com/ontology/principles/architecture-category-transactions-state-concurrency.md)