# [Financial Crime](../domain.md)

## Entities

### Exchange Rate

An Exchange Rate records conversion values between a source and target currency at a specific effective time.

```mermaid
---
config:
  layout: elk
---
classDiagram
  class ExchangeRate{
    * Exchange Rate Identifier : string
    Rate Value : decimal
    Effective Date Time : datetime
  }

  ExchangeRate "0..*" --> "1" Currency : base
  ExchangeRate "0..*" --> "1" Currency : quote

  class Currency["<a href='https://github.com/Semprini/md-ddl/blob/main/examples/Financial%20Crime/entities/currency.md'>Currency</a>"]
```

```yaml
existence: dependent
mutability: append_only
attributes:
  Exchange Rate Identifier:
    type: string
    identifier: primary
    description: Unique identifier for the exchange rate observation.

  Rate Value:
    type: decimal
    description: Conversion multiplier from base to quote currency.

  Effective Date Time:
    type: datetime
    description: Timestamp at which the rate became effective.
```

```yaml
governance:
  retention_basis: Inherited from domain default retention of 10 years post relationship end for AML/CTF record-keeping
```

## Relationships

### Exchange Rate References Base Currency

Each Exchange Rate references one base Currency.

```yaml
source: Exchange Rate
type: references
target: Currency
cardinality: many-to-one
granularity: atomic
ownership: Exchange Rate
```

### Exchange Rate References Quote Currency

Each Exchange Rate references one quote Currency.

```yaml
source: Exchange Rate
type: references
target: Currency
cardinality: many-to-one
granularity: atomic
ownership: Exchange Rate
```