# Semantic Conventions for mobile events

**Status**: [Experimental][DocumentStatus]

This document defines semantic conventions for instrumentations that emit events on mobile platforms.
All mobile events MUST set `event.domain` as `device`.

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- [Lifecycle instrumentation](#lifecycle-instrumentation)
  * [iOS](#ios)
  * [Android](#android)

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## Lifecycle instrumentation

This section defines how to apply semantic conventions when instrumenting application lifecycle.
This event is meant to be used in conjunction with `os.name` [resource semantic convention](/docs/resource/os.md) to identify the mobile operating system (e.g. Android, iOS).

### iOS

<!-- semconv ios.lifecycle.events -->
The event name MUST be `app.lifecycle`.

| Attribute  | Type | Description  | Examples  | Requirement Level |
|---|---|---|---|---|
| `ios.state` | string | This attribute represents the state the application has transitioned into at the occurrence of the event. [1] | `active` | Required |

**[1]:** The iOS lifecycle states are defined in the [UIApplicationDelegate documentation](https://developer.apple.com/documentation/uikit/uiapplicationdelegate#1656902), and from which the `OS terminology` column values are derived.

`ios.state` MUST be one of the following:

| Value  | Description |
|---|---|
| `active` | The app has become `active`. Associated with UIKit notification `applicationDidBecomeActive`. |
| `inactive` | The app is now `inactive`. Associated with UIKit notification `applicationWillResignActive`. |
| `background` | The app is now in the background. This value is associated with UIKit notification `applicationDidEnterBackground`. |
| `foreground` | The app is now in the foreground. This value is associated with UIKit notification `applicationWillEnterForeground`. |
| `terminate` | The app is about to terminate. Associated with UIKit notification `applicationWillTerminate`. |
<!-- endsemconv -->

### Android

<!-- semconv android.lifecycle.events -->
The event name MUST be `app.lifecycle`.

| Attribute  | Type | Description  | Examples  | Requirement Level |
|---|---|---|---|---|
| `android.state` | string | This attribute represents the state the application has transitioned into at the occurrence of the event. [1] | `created` | Required |

**[1]:** The Android lifecycle states are defined in [Activity lifecycle callbacks](https://developer.android.com/guide/components/activities/activity-lifecycle#lc), and from which the `OS identifiers` are derived.

`android.state` MUST be one of the following:

| Value  | Description |
|---|---|
| `created` | Any time before Activity.onResume() or, if the app has no Activity, Context.startService() has been called in the app for the first time. |
| `background` | Any time after Activity.onPause() or, if the app has no Activity, Context.stopService() has been called when the app was in the foreground state. |
| `foreground` | Any time after Activity.onResume() or, if the app has no Activity, Context.startService() has been called when the app was in either the created or background states. |
<!-- endsemconv -->

[DocumentStatus]: https://github.com/open-telemetry/opentelemetry-specification/tree/v1.22.0/specification/document-status.md
