---
title: "ModelFlow"
description: "one flow of a systems model between two stocks, its rate a driver tree the one evaluator computes each step"
section: concepts
address: /concepts/modelflow
contract: 0476e35e6e275db5
---

# ModelFlow

one flow of a systems model between two stocks, its rate a driver tree the one evaluator computes each step

[figure: ModelFlow is a value at none scope. The drawing shows its fields and the objects that they point at.]

| property | value |
|---|---|
| kind | value |
| scope | none |
| key | none |
| store | none |
| family | market |



## Fields


| field | type | required | note |
|---|---|---|---|
| `name` | `text` | yes |  |
| `from_stock` | `text` | yes |  |
| `to_stock` | `text` | yes |  |
| `rate` | [DriverNode](/concepts/drivernode) | yes | the units that move per step, as a tree over drivers |
| `roles` | [RoleAroundADecision](/concepts/rolearoundadecision) | yes | the roles that hand the unit on |
| `shape` | [CalculationShape](/concepts/calculationshape) | no | the calculation shape the flow's money follows, where it carries money |
| `selects` | `text` | no | the predicate, by name, that selects the units the flow moves |
| `delay` | `duration` | no | the delay before a moved unit counts |



## Routes that use it
No route takes or returns ModelFlow directly. The record holds it, and the objects that point at it reach it.