# Inputs and outputs

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***

**Added in** `eventcatalog@3.8.0`

Data products consume inputs (e.g events, services, data stores, channels) and produce outputs (e.g events, services, data stores, channels). Defining these relationships helps teams understand data lineage and dependencies.

## Defining inputs (input ports)[​](#defining-inputs-input-ports "Direct link to Defining inputs (input ports)")

Inputs represent the source dependencies your data product consumes. In EventCatalog these can be [events](/docs/development/guides/messages/events/introduction.md), commands, queries, [services](/docs/development/guides/services/introduction.md), [data stores](/docs/development/guides/data/introduction.md), or [channels](/docs/development/guides/channels/introduction.md).

You need to specify the `id` of the input and optionally the `version` of the input. If no version is provided the latest version will be used.

```
---
id: order-analytics
name: Order Analytics
version: 1.0.0

# Define input dependencies
inputs:
  - id: OrderConfirmed
  - id: PaymentProcessed
  - id: FraudDetectionService
  - id: payment-cache
  - id: payment-domain-eventbus
---
```

## Defining outputs[​](#defining-outputs "Direct link to Defining outputs")

Outputs represent what your data product produces. These can be events, commands, queries, services, data stores, or channels.

You need to specify the `id` of the output and optionally the `version` of the output. If no version is provided the latest version will be used.

```
---
id: order-analytics
name: Order Analytics
version: 1.0.0

# Define what this data product produces
outputs:
  - id: OrderMetricsCalculated
  - id: NotificationService
  - id: orders-db
  - id: orders-domain-eventbus
---
```

## Visualizing relationships[​](#visualizing-relationships "Direct link to Visualizing relationships")

The `<NodeGraph />` component automatically visualizes inputs and outputs.

```
<NodeGraph />
```

![Example](/assets/images/data-product-node-graph-ce9c235d434fc7ba57d0708426081a1f.png)

This graph shows:

* Input events flowing into the data product
* Output events or data stores produced
* Services that interact with the data product
* Contract relationships for data stores

## Complete example[​](#complete-example "Direct link to Complete example")

/data-products/PaymentAnalytics/index.mdx

```
---
id: payment-analytics
name: Payment Analytics
version: 1.0.0
summary: Payment performance metrics and fraud insights

inputs:
  - id: PaymentInitiated
  - id: PaymentProcessed
  - id: PaymentFailed
  - id: FraudCheckCompleted
  - id: PaymentService
  - id: payments-db

outputs:
  - id: NotificationService
  - id: payment-domain-eventbus
  - id: payment-analytics-db
    contract:
      path: payment-metrics-contract.json
      name: Payment Metrics Contract
      type: json-schema
---

## Overview

Payment Analytics transforms payment lifecycle events into comprehensive metrics.

<NodeGraph />

## Input Events

- **PaymentInitiated** - Start of payment flow (~60k/day)
- **PaymentProcessed** - Successful payments (~55k/day)
- **PaymentFailed** - Failed transactions (~5k/day)
- **FraudCheckCompleted** - Fraud detection results (~60k/day)

## Output Tables

### fact_payments

Transaction-level payment data with fraud scores.

<SchemaViewer file="payment-metrics-contract.json" />
```

## Next steps[​](#next-steps "Direct link to Next steps")

* [Add schema contracts](/docs/development/guides/data-products/contracts.md)
* [Version data products](/docs/development/guides/data-products/versioning.md)
* [Add to domains](/docs/development/guides/data-products/adding-to-domains.md)