# Enum: ConnectivityRule 




_Rule for expanding a population-level Edge into individual cell-to-cell connections. Names a connectivity pattern between the source and target populations so a network of populations declares its projections once, without enumerating every connection; each backend expands the rule into its native connection set (e.g. the NeuroML exporter emits one <projection> with size_src x size_tgt <connection> elements). Backend-independent: it states the connectivity pattern, not how any simulator stores it._



<div data-search-exclude markdown="1">

URI: [tvbo:enum/ConnectivityRule](https://w3id.org/tvbo/enum/ConnectivityRule)

## Permissible Values
| Value | Meaning | Description |
| --- | --- | --- |
| all_to_all | None | Fully connected projection: every source cell connects to every target cell |
| one_to_one | None | Index-aligned projection: source cell i connects to target cell i (min of the... |
| random | None | Sparse random projection (fixed-probability Erdos-Renyi): each of the size_sr... |




## Slots

| Name | Description |
| ---  | --- |
| [connectivity](../slots/connectivity.qmd) | Connectivity rule for a population-level Edge |










## Identifier and Mapping Information





### Schema Source


* from schema: https://w3id.org/tvbo






## LinkML Source

<details>
```yaml
name: ConnectivityRule
description: 'Rule for expanding a population-level Edge into individual cell-to-cell
  connections. Names a connectivity pattern between the source and target populations
  so a network of populations declares its projections once, without enumerating every
  connection; each backend expands the rule into its native connection set (e.g. the
  NeuroML exporter emits one <projection> with size_src x size_tgt <connection> elements).
  Backend-independent: it states the connectivity pattern, not how any simulator stores
  it.'
from_schema: https://w3id.org/tvbo
rank: 1000
permissible_values:
  all_to_all:
    text: all_to_all
    description: 'Fully connected projection: every source cell connects to every
      target cell. For a self-projection (same source and target population) the diagonal
      i->i is governed by the Edge''s allow_self_connections flag.'
  one_to_one:
    text: one_to_one
    description: 'Index-aligned projection: source cell i connects to target cell
      i (min of the two population sizes).'
  random:
    text: random
    description: 'Sparse random projection (fixed-probability Erdos-Renyi): each of
      the size_src x size_tgt possible connections is present independently with probability
      given by the Edge''s `connection_probability` parameter (in `Edge.parameters`,
      alongside `weight`). For a self-projection the diagonal i->i is governed by
      Edge.allow_self_connections. A backend that only supports dense projections
      may reject this rule rather than approximate it.'

```
</details>

</div>