# Asset domains and collections

> What an asset domain is: a domain that stands for a physical or digital resource, what it holds, and how assets are grouped into collections.

An asset domain is a domain that stands for a resource with measurable value: a building, a piece
of land, a vehicle, a device, a dataset or a piece of software. It is a kind of
[digital twin domain](/articles/cdt-systems), and like every domain it has an ownable entity, a
DID, an on-chain record (its IID document) and the other parts listed in
[Core concepts](/core-concepts#who-takes-part).

Read this page to see how assets are represented and grouped. For the record's fields and how to
create one, use [Digital twins](/guides/digital-twins).

## Kinds of asset

| Kind | Examples |
| --- | --- |
| Physical | Buildings, land, vehicles, infrastructure |
| Digital | Software, datasets, digital media |
| Mixed | Assets that combine physical and digital parts |

## What an asset domain holds

| Part | What it does for an asset |
| --- | --- |
| Entity | An NFT that can be owned and transferred, so ownership of the asset is recorded on chain |
| DID and IID document | The asset's identifier, and its record of keys, controllers and service endpoints |
| Services | Endpoints that take in data from sensors, remote feeds or people |
| Matrix space and VFS | An encrypted data store for the asset's data, built on the Matrix protocol, which can be shared with other domains |
| Linked claims | Signed records of events and data about the asset |

Claims about an asset are decided like any other claim: a decision oracle produces the facts and
the IXO decision engine applies the rules. A decided outcome can be issued as a verifiable
credential. A signed claim about an asset shows who said what about it. It does not show that it
is true. See [What each record proves](/trust-boundaries).

## Asset collections

Assets can be grouped into collections, and a collection is itself a domain. Collections are used
for portfolios, projects, funds and programmes; for geographic groups such as countries, regions,
cities and neighbourhoods; for infrastructure such as buildings, facilities, equipment and
vehicles; and for digital resources such as software, data, media and design assets.

## Where to go next

<CardGroup cols={2}>
  <Card title="Digital twins" icon="cube" href="/guides/digital-twins">
    The record's fields, example code, and creating a twin from a protocol.
  </Card>
  <Card title="Manage entities" icon="diagram-project" href="/guides/dev/entities">
    Create the entity at an asset's core and transfer its ownership.
  </Card>
</CardGroup>