This page specifies metadata attributes that _must_ be included, and that _may_ be included. These attributes are organized hierarchically, from top-layer attributes like `"main"` to sub-level attributes like `"main.type"`. This page also provides DDO metadata examples.
Ocean Aquarius helps manage metadata. It can be used to write DDOs to the chain, read from the chain, and has a local cache of the DDO in plaintext with fast search.
| **`name`** | Text |**Yes** | Descriptive name or title of the asset. |
| **`type`** | Text |**Yes** | Asset type. Includes `"dataset"` (e.g. csv file), `"algorithm"` (e.g. Python script). Each type needs a different subset of metadata attributes. |
| **`author`** | Text |**Yes** | Name of the entity generating this data (e.g. Tfl, Disney Corp, etc.). |
| **`license`** | Text |**Yes** | Short name referencing the license of the asset (e.g. Public Domain, CC-0, CC-BY, No License Specified, etc. ). If it's not specified, the following value will be added: "No License Specified". |
| **`files`** | Array of files object |**Yes** | Array of `File` objects including the encrypted file urls. |
| **`dateCreated`** | DateTime |**Yes** | The date on which the asset was created by the originator. ISO 8601 format, Coordinated Universal Time, e.g. `2019-01-31T08:38:32Z`. |
| **`url`** | Local | Content URL. Omitted from the remote metadata. Supports `http(s)://` and `ipfs://` URLs. |
| **`name`** | No | File name. |
| **`checksum`** | No | Checksum of the file using your preferred format (i.e. MD5). Format specified in `checksumType`. If it's not provided can't be validated if the file was not modified after registering. |
| **`checksumType`** | No | Format of the provided checksum. Can vary according to server (i.e Amazon vs. Azure) |
| **`contentLength`** | No | Size of the file in bytes. |
| **`encoding`** | No | File encoding (e.g. UTF-8). |
| **`compression`** | No | File compression (e.g. no, gzip, bzip2, etc). |
| **`encrypted`** | No | Boolean. Is the file encrypted? If is not set is assumed the file is not encrypted |
| **`encryptionMode`** | No | Encryption mode used. Just valid if `encrypted=true` |
| **`resourceId`** | No | Remote identifier of the file in the external provider. It is typically the remote id in the cloud provider. |
| **`attributes`** | No | Key-Value hash map with additional attributes describing the asset file. It could include details like the Amazon S3 bucket, region, etc. |
| **`isListed`** | Boolean | No | Use to flag unsuitable content. True by default. If it's false, the content must not be returned. |
| **`isRetired`** | Boolean | No | Flag retired content. False by default. If it's true, the content may either not be returned, or returned with a note about retirement. |
| **`isOrderDisabled`** | Boolean | No | For temporarily disabling ordering assets, e.g. when file host is in maintenance. False by default. If it's true, no ordering of assets for download or compute should be allowed. |
| **`tags`** | Array of Text | No | Array of keywords or tags used to describe this content. Empty by default. |
| **`description`** | Text | No | Details of what the resource is. For a dataset, this attribute explains what the data represents and what it can be used for. |
| **`copyrightHolder`** | Text | No | The party holding the legal copyright. Empty by default. |
| **`workExample`** | Text | No | Example of the concept of this asset. This example is part of the metadata, not an external link. |
| **`links`** | Array of Link | No | Mapping of links for data samples, or links to find out more information. Links may be to either a URL or another Asset. We expect marketplaces to converge on agreements of typical formats for linked data: The Ocean Protocol itself does not mandate any specific formats as these requirements are likely to be domain-specific. The links array can be an empty array, but if there is a link object in it, then an "url" is required in that link object. |
| **`inLanguage`** | Text | No | The language of the content. Please use one of the language codes from the [IETF BCP 47 standard](https://tools.ietf.org/html/bcp47). |
| **`updateFrequency`** | An indication of update latency - i.e. How often are updates expected (seldom, annually, quarterly, etc.), or is the resource static that is never expected to get updated. |
| **`structuredMarkup`** | A link to machine-readable structured markup (such as ttl/json-ld/rdf) describing the dataset. |
This is what the DDO metadata looks like. All fields are in plaintext. This is before it's stored on-chain or when it's retrieved and decrypted into a local cache.
