The Home APIs for Android present all devices in the Google Home ecosystem in a
unified data model. This data model covers all types of devices (from Google
Nest or 3rd party manufacturers), regardless of the underlying smart home
technology (such as Matter or Cloud-to-cloud),
and provides a common API surface to build user experiences for both
smart home and mobile app developers.

## Device types

The device types presented in the Home APIs are a unification of
Matter and Cloud-to-cloud data models. Some are
derived directly from Matter, some are an extension of
Matter device types, and some are derived from
Cloud-to-cloud.

Device types contain traits that are used to control and manage devices. Like
device types, traits are derived from Matter clusters and
Cloud-to-cloud traits and presented in a common format that is
similar to that of Matter clusters. In the Home APIs,
Matter-derived traits are called *traits* , not *clusters*.

As such, device types and traits in the Home APIs are intended to be
Matter-first. A Matter device type or
trait takes precedence over a Cloud-to-cloud analog.

See [Supported device types on Android](https://developers.home.google.com/apis/android/supported-device-types)
for a list of device types and their traits.

## Traits

Kotlin versions of traits are generated for use in the Home APIs, and contain
additional features specific to the Home APIs (not found in
Matter or Cloud-to-cloud). For example, each
trait has methods to check whether a trait supports a specific attribute or
command. This is useful when determining whether reading of state or certain
actions can be carried out on a user's device, since not all devices in a device
type are expected to have all the same features.

Each trait is contained in its own namespace and must be imported individually
for use.

For example, to use the Matter On/Off trait and On/Off
Plug-in Unit device type, import the following packages into your application:  

    import com.google.home.matter.standard.OnOff
    import com.google.home.matter.standard.OnOffPluginUnitDevice

For a [Garage device
type](https://developers.home.google.com/reference/kotlin/com/google/home/google/GoogleGarageDevice)
(from the Google smart home), include a mix of Matter and
Google traits:  

    import com.google.home.google.LockUnlock
    import com.google.home.matter.standard.DoorLock
    import com.google.home.matter.standard.GoogleGarageDevice

Android Studio has auto-complete functionality and will often
handle the full package names for you when adding `import` lines to source files
in your project. However, package names are not consistent across all device
types and traits. See the reference to verify the correct package name for each
[`DeviceType`](https://developers.home.google.com/reference/kotlin/com/google/home/DeviceType) or
[`Trait`](https://developers.home.google.com/reference/kotlin/com/google/home/Trait).

<br />

| **Tip:** Device types that begin with `Google*` are Google smart home device types and are not Google-branded devices (such as Google TV).

<br />

Most traits are supported for use with Automations, and some traits are *only*
available for Automations. For more details, see [Automation API trait support
on Android](https://developers.home.google.com/apis/android/automation/supported-traits).

## Device type composition

The Home APIs support most Matter application clusters
as traits in the data model. Traits that don't correspond to device control or
states and don't offer any utility for end users, such as Binding and
Groups, are not exposed through the Home APIs.

Traits derived from Cloud-to-cloud smart home traits typically have
the same name between Cloud-to-cloud and the Home APIs, such as in
the example of OpenClose. Others are represented as extensions of
Matter traits, created using Matter
manufacturer-specific extensions. These traits bridge the gap for a
smart home trait where functionality is split between the
Matter SDK and the Google Home ecosystem. A specific
example of this are the `Google*` device types which come from
Cloud-to-cloud but don't have Matter analogs yet.

Device types are composed of traits from one or both sources,
Matter or Cloud-to-cloud.

For example, the [Fan device
type](https://developers.home.google.com/reference/kotlin/com/google/home/matter/standard/FanDevice) is composed
of both and features three traits:

- The `Identify` Matter trait provides all the functionality from the Matter `Identify`.
- The `FanControl` Matter trait provides all the functionality from the Matter `FanControl` trait
- The `ExtendedFanControl` Google trait provides all the functionality from the Google smart home `FanSpeed` trait that is not covered by the `FanControl` Matter trait

This type of trait composition provides a flexible model for complete device
type functionality, abstracting the underlying smart home data
models.