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Feature: OEPS - Add DID and Asset DDO markdowns

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# OEP-8: Assets Metadata Ontology
```
shortname: 8/ASSET-DDO
name: Assets Metadata Ontology
type: Standard
status: Draft
version: 0.5
editor: Alex Coseru <alex@oceanprotocol.com>
contributors: Aitor Argomaniz <aitor@oceanprotocol.com>
Enrique Ruiz <enrique@oceanprotocol.com>,
Matthias Kretschmann <matthias@oceanprotocol.com>,
Jose Pablo Fernandez <jose@oceanprotocol.com>,
Marcus Jones <marcus@oceanprotocol.com>,
Troy McConaghy <troy@oceanprotocol.com>
```
**Table of Contents**
- [Motivation](#motivation)
- [Life Cycle of Metadata](#life-cycle-of-metadata)
- [Local Metadata](#local-metadata)
- [Remote Metadata](#remote-metadata)
- [Metadata Attributes](#metadata-attributes)
- [Main Attributes](#main-attributes)
- [File Attributes](#file-attributes)
- [Additional Attributes](#additional-attributes)
- [Other Suggested Additional Attributes](#other-suggested-additional-attributes)
- [Status Attributes](#status-attributes)
- [Example of Local Metadata](#example-of-local-metadata)
- [Example of Remote Metadata](#example-of-remote-metadata)
- [Specific attributes per asset type](#specific-attributes-per-asset-type)
- [Algorithm attributes](#algorithm-attributes)
- [References](#references)
- [Change Process](#change-process)
- [Language](#language)
---
## Motivation
Every asset (dataset, algorithm) in the Ocean Network has an associated Decentralized Identifier (DID) and DID document / DID Descriptor Object (DDO). Because assets without proper descriptive metadata have poor visibility and discoverability.
See [OEP 7/DID](../../7/) for information about the overall structure of Ocean DDOs and DIDs.
This OEP is about one particular part of Ocean DDOs: the asset metadata, a JSON object with information about the asset.
This OEP defines the assets metadata ontology, i.e. the schema for the asset metadata. It's based on the public schema.org [DataSet schema](https://schema.org/Dataset).
This OEP doesn't detail the exact method of registering assets on-chain or storing DDOs.
The main motivations of this OEP are to:
- Specify the common attributes that MUST be included in any asset metadata stored in the Ocean Network
- Normalize the attributes to use in any curation process, to provide a common structure to sort and filter the DDOs
- Identify the recommended additional attributes that SHOULD be included in a DDO to facilitate asset search
- Provide an example of an asset metadata object and additional links for reference
## Life Cycle of Metadata
### Local Metadata
Metadata is first created by the publisher of the asset. The publisher has knowledge of the file URLs, and they are stored in plaintext in the `files` object. This initial metadata is the _local metadata_.
### Remote Metadata
A publisher publishes (registers) an asset using [Ocean-lib](https://docs.oceanprotocol.com/concepts/components/#squid-libraries), which might be running on their local machine or remotely. When they do, the local metadata is passed to Squid, which makes some changes and additions in the metadata, puts it into a DDO, and sends that DDO to a metadata store (Aquarius).
Aquarius may also make some changes and additions to the metadata, such as the `datePublished` or parts of the `curation` object. The metadata that finally gets stored by Aquarius is the _remote metadata_.
> A marketplace can and might also act as a publisher. [OEP-11](../../11) describes the publishing flow in more detail.
## Metadata Attributes
An asset is the representation of different type of resources in Ocean Protocol. Typically can asset could be one of the following asset types:
- _Dataset_. An asset representing a dataset or data resource. It could be for example a CSV file or a multiple JPG files.
- _Algorithm_. An asset representing a piece of software. It could be a python script using tensorflow, a spark job, etc.
Each kind of asset require a different subset of metadata attributes. The distintion between the type of asset (dataset, algorithm) is given by the attribute `DDO.services["metadata"].main.type`
A `metadata` object has the following attributes, all of which are objects.
| Attribute | Required | Description |
| --------------------------- | -------- | ---------------------------------------------------------- |
| **`main`** | Yes | Main attributes used to calculate the service checksum |
| **`status`** | No. | Status attributes |
| **`additionalInformation`** | No | Optional attributes |
| **`encryptedFiles`** | (remote) | Encrypted string of the `attributes.main.files` object. |
| **`encryptedServices`** | (remote) | Encrypted string of the `attributes.main.services` object. |
The `main`, `curation` and `additionalInformation` attributes are independent of the asset type, all assets have those metadata sections.
### Main Attributes
**This list of attributes can't be modified after creation**, because these are considered as the metadata essence of the asset created. This information is used to calculate the unique checksum of the asset. If any change would be necessary in the following attributes, it would be necessary to create a new asset derived from the existing one.
The `main` object has the following attributes, not all are required. Some are required by only the metadata store (_remote_) and others are mandatory for _local_ metadata only. If required or not by both, they are marked with _Yes/No_ in the _Required_ column.
| Attribute | Type | Required | Description |
| ------------------- | --------------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`name`** | Text | Yes | Descriptive name or title of the asset. |
| **`type`** | Text | Yes | Type of the asset. Helps to filter by the type of asset. It could be for example ("dataset", "algorithm"). |
| **`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`. |
| **`datePublished`** | DateTime | (remote) | The date on which the asset DDO is registered into the metadata store (Aquarius) |
| **`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. Further metadata about each file is stored, see [File Attributes](#file-attributes) |
#### File Attributes
File attributes are a subset of the `main` section.
A file object has the following attributes, with the details necessary to consume and validate the data.
| Attribute | Required | Description |
| -------------------- | -------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`url`** | (local) | Content URL. Omitted from the remote metadata. Supports `http(s)://` and `ipfs://` URLs. |
| **`name`** | no | File name. |
| **`index`** | yes | Index number starting from 0 of the file. |
| **`contentType`** | yes | File format. |
| **`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. |
### Additional Attributes
All the additional information will be stored as part of the `additionalInformation` section.
| Attribute | Type | Required |
| --------------------- | ------------- | -------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`categories`** | Array of Text | No | Optional array of categories associated to the asset. |
| **`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). |
#### Other Suggested Additional Attributes
These are examples of attributes that can enhance the discoverability of a resource:
| Attribute | Description |
| ---------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`sla`** | Service Level Agreement. |
| **`industry`** | |
| **`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. |
| **`termsOfService`** | |
| **`privacy`** | |
| **`keyword`** | A list of keywords/tags describing a dataset. |
| **`structuredMarkup`** | A link to machine-readable structured markup (such as ttl/json-ld/rdf) describing the dataset. |
The publisher of a DDO MAY add additional attributes or change the above object definition.
### Status Attributes
A `status` object has the following attributes.
| Attribute | Type | Required | Description |
| --------------------- | ------- | -------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **`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. |
## Example of Local Metadata
```json
{
"main": {
"name": "Madrid Weather forecast",
"dateCreated": "2019-05-16T12:36:14.535Z",
"author": "Norwegian Meteorological Institute",
"type": "dataset",
"license": "Public Domain",
"price": "123000000000000000000",
"files": [
{
"index": 0,
"url": "https://example-url.net/weather/forecast/madrid/350750305731.xml",
"contentLength": "0",
"contentType": "text/xml",
"compression": "none"
}
]
},
"additionalInformation": {
"description": "Weather forecast of Europe/Madrid in XML format",
"copyrightHolder": "Norwegian Meteorological Institute",
"categories": ["Other"],
"links": [],
"tags": [],
"updateFrequency": null,
"structuredMarkup": []
},
"status": {
"isListed": true,
"isRetired": false,
"isOrderDisabled": false
}
}
```
## Example of Remote Metadata
Similarly, this is how the metadata file would look as a response to querying Aquarius (remote metadata). Note that `url` is removed from all objects in the `files` array, and `encryptedFiles` & `curation` are added.
```json
{
"service": [
{
"index": 0,
"serviceEndpoint": "http://aquarius:5000/api/v1/aquarius/assets/ddo/{did}",
"type": "metadata",
"attributes": {
"main": {
"type": "dataset",
"name": "Madrid Weather forecast",
"dateCreated": "2019-05-16T12:36:14.535Z",
"author": "Norwegian Meteorological Institute",
"license": "Public Domain",
"files": [
{
"contentLength": "0",
"contentType": "text/xml",
"compression": "none",
"index": 0
}
],
"datePublished": "2019-05-16T12:41:01Z"
},
"encryptedFiles": "0x7a0d1c66ae861…df43aa9",
"additionalInformation": {
"description": "Weather forecast of Europe/Madrid in XML format",
"copyrightHolder": "Norwegian Meteorological Institute",
"categories": ["Other"],
"links": [],
"tags": [],
"updateFrequency": null,
"structuredMarkup": []
},
"status": {
"isListed": true,
"isRetired": false,
"isOrderDisabled": false
}
}
}
]
}
```
### Specific attributes per asset type
Depending on the asset type (dataset, algorithm), there are different metadata attributes supported:
#### Algorithm attributes
An asset of type `algorithm` has the following additional attributes under `main.algorithm`:
| Attribute | Type | Required | Description |
| --------------- | -------- | -------- | --------------------------------------------- |
| **`language`** | `string` | no | Language used to implement the software |
| **`format`** | `string` | no | Packaging format of the software. |
| **`version`** | `string` | no | Version of the software. |
| **`container`** | `Object` | yes | Object describing the Docker container image. |
The `container` object has the following attributes:
| Attribute | Type | Required | Description |
| ---------------- | -------- | -------- | ----------------------------------------------------------------- |
| **`entrypoint`** | `string` | yes | The command to execute, or script to run inside the Docker image. |
| **`image`** | `string` | yes | Name of the Docker image. |
| **`tag`** | `string` | yes | Tag of the Docker image. |
| **`checksum`** | `string` | yes | Checksum of the Docker image. |
```json
{
"index": 0,
"serviceEndpoint": "http://localhost:5000/api/v1/aquarius/assets/ddo/{did}",
"type": "metadata",
"attributes": {
"main": {
"author": "John Doe",
"dateCreated": "2019-02-08T08:13:49Z",
"license": "CC-BY",
"name": "My super algorithm",
"type": "algorithm",
"algorithm": {
"language": "scala",
"format": "docker-image",
"version": "0.1",
"container": {
"entrypoint": "node $ALGO",
"image": "node",
"tag": "10",
"checksum": "efb2c764274b745f5fc37f97c6b0e761"
}
},
"files": [
{
"name": "build_model",
"url": "https://raw.githubusercontent.com/oceanprotocol/test-algorithm/master/javascript/algo.js",
"index": 0,
"checksum": "efb2c764274b745f5fc37f97c6b0e761",
"contentLength": "4535431",
"contentType": "text/plain",
"encoding": "UTF-8",
"compression": "zip"
}
]
},
"additionalInformation": {
"description": "Workflow to aggregate weather information",
"tags": ["weather", "uk", "2011", "workflow", "aggregation"],
"copyrightHolder": "John Doe"
}
}
}
```
#### Compute datasets attributes
An asset with a service of type `compute` has the following additional attributes under `main.privacy`:
| Attribute | Type | Required | Description |
| --------------------------------- | ------------------ | -------- | ---------------------------------------------------------- |
| **`allowRawAlgorithm`** | `boolean` | yes | If True, a drag & drop algo can be runned |
| **`allowNetworkAccess`** | `boolean` | yes | If True, the algo job will have network access (stil WIP) |
| **`publisherTrustedAlgorithms `** | Array of `Objects` | yes | If Empty , then any published algo is allowed. (see below) |
The `publisherTrustedAlgorithms ` is an array of objects with the following structure:
| Attribute | Type | Required | Description |
| ------------------------------ | -------- | -------- | ------------------------------------------------------------------ |
| **`did`** | `string` | yes | The did of the algo which is trusted by the publisher. |
| **`filesChecksum`** | `string` | yes | Hash of ( algorithm's encryptedFiles + files section (as string) ) |
| **`containerSectionChecksum`** | `string` | yes | Hash of the algorithm container section (as string) |
To produce filesChecksum:
```
sha256(algorithm_ddo.service['metadata'].attributes.encryptedFiles + JSON.Stringify(algorithm_ddo.service['metadata'].attributes.main.files) )
```
To produce containerSectionChecksum:
```
sha256(JSON.Stringify(algorithm_ddo.service['metadata'].attributes.main.algorithm.container))
```
Example of a compute service
```json
{
"type": "compute",
"index": 1,
"serviceEndpoint": "https://provider.oceanprotocol.com",
"attributes": {
"main": {
"name": "dataAssetComputingService",
"creator": "0xA32C84D2B44C041F3a56afC07a33f8AC5BF1A071",
"datePublished": "2021-02-17T06:31:33Z",
"cost": "1",
"timeout": 3600,
"privacy": {
"allowRawAlgorithm": true,
"allowNetworkAccess": false,
"publisherTrustedAlgorithms": [
{
"did": "0xxxxx",
"filesChecksum": "1234",
"containerSectionChecksum": "7676"
},
{
"did": "0xxxxx",
"filesChecksum": "1232334",
"containerSectionChecksum": "98787"
}
]
}
}
}
}
```
## References
[Schema.org](https://schema.org/) is a collaborative, community activity with a mission to create, maintain, and promote schemas for structured data on the Internet. Data types use the [Schema.org primitive data types](https://schema.org/DataType).
- [Schema.org: DataSet](https://schema.org/Dataset)
- [Schema.org: FileSize](https://schema.org/fileSize)
- [Common license types for datasets](https://help.data.world/hc/en-us/articles/115006114287-Common-license-types-for-datasets)
## Change Process
This document is governed by [OEP 2/COSS](../2/README.md).
## Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [BCP 14](https://tools.ietf.org/html/bcp14) \[[RFC2119](https://tools.ietf.org/html/rfc2119)\] \[[RFC8174](https://tools.ietf.org/html/rfc8174)\] when, and only when, they appear in all capitals, as shown here.

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# OEP-7: Decentralized Identifiers
```
shortname: 7/DID
name: Decentralized Identifiers
type: Standard
status: Draft
version: 0.3
editor: Alex Coseru <alex@oceanprotocol.com>
contributors: Matthias Kretschmann <matthias@oceanprotocol.com>,
Ahmed Ali <ahmed@oceanprotocol.com>
```
**Table of Contents**
- [Motivation](#motivation)
- [Specification](#specification)
- [Proposed Solution](#proposed-solution)
- [Decentralized IDs (DIDs)](#decentralized-ids-dids)
- [DID Documents (DDOs)](#did-documents-ddos)
- [DDO Services](#ddo-services)
- [Credentials](#credentials)
- [Integrity](#integrity)
- [How to compute the integrity checksum](#how-to-compute-the-integrity-checksum)
- [DID Document Proof](#did-document-proof)
- [Length of a DID](#length-of-a-did)
- [How to compute a DID](#how-to-compute-a-did)
- [References](#references)
- [Change Process](#change-process)
- [Language](#language)
---
This specification is based on:
- the [W3C DID specification](https://w3c-ccg.github.io/did-spec/), which was at version 0.11 as of August 2018,
- the [Ocean Protocol technical whitepaper](https://github.com/oceanprotocol/whitepaper),
- [3/ARCH](../3/README.md), and
- [4/AGENT](../4/README.md).
## Motivation
The main motivations of this OEP are:
- Design a solution to extend the current architecture to use **Decentralized Identifiers (DIDs)** and **DID Documents (DDOs)**
- Understand how to resolve DIDs into DDOs
- Establishing the mechanism to know if the DDO associated with a DID was modified
- Defining the common mechanisms, interfaces and APIs to implemented the designed solution
- Define how Ocean assets, agents and domains can be modeled with a DID/DDO data model
- Understand how DID hubs are formed, and how they integrate a business and storage layer
## Specification
Requirements are:
- The DID resolving capabilities MUST be exposed in the client libraries, enabling to resolve a DDO directly in a totally transparent way
- ASSETS are DATA objects describing RESOURCES under control of a PUBLISHER
- PROVIDERS store the ASSET metadata off-chain
- OCEAN doesn't store ASSET contents (e.g. files)
- An ASSET is modeled in OCEAN as off-chain information stored in AQUARIUS
- ASSETS information only can be modified by OWNERS or DELEGATED USERS
- ASSETS can be resolved using a Decentralized ID (DID)
- A DID Document (DDO) should include the ASSET metadata
- Any kind of object registered in Ocean SHOULD have a DID allowing one to uniquely identify that object in the system
- ASSET DDO (and the metadata included as part of the DDO) is associated to the ASSET information stored using a common DID
- A DID can be resolved to get access to a DDO
- The function to calculate the HASH MUST BE standard
## Proposed Solution
### Decentralized IDs (DIDs)
A DID is a unique identifier that can be resolved or de-referenced to a standard resource describing the entity (a DID Document or DDO).
If we apply this to Ocean, the DID would be the unique identifier of an object represented in Ocean (i.e. the Asset ID of an ASSET or the Actor ID of a USER).
The DDO SHOULD include the METADATA information associated with this object.
The DDO is stored off-chain in Ocean.
In Ocean, a DID is a string that looks like:
```text
did:op:0ebed8226ada17fde24b6bf2b95d27f8f05fcce09139ff5cec31f6d81a7cd2ea
```
which follows [the generic DID scheme](https://w3c-ccg.github.io/did-spec/#the-generic-did-scheme).
Details about how to compute the DID are given below.
### DID Documents (DDOs)
If a DID is the index key in a key-value pair, then the DID Document is the value to which the index key points.
The combination of a DID and its associated DID Document forms the root record for a decentralized identifier.
![DDO Content](images/ddo-content.png)
A DDO document is composed of standard DDO attributes:
- `@context`
- `id`
- `created`
- `updated`
- `publicKey`
- `authentication`
- `proof`
- `verifiableCredential`
- `dataToken`
- `service`
- `credentials` - optional flag, which describes the credentials needed to access a dataset (see below)
Asset metadata must be included as one of the objects inside the `"service"` array, with type `"metadata"`.
#### DDO Services
Each type of asset (dataset, algorithm, workflow, etc, ..) typically will have associated different kind of services. There are multiple type of services that are commonly added to all the assets:
- metadata - describing the asset
- provenance - describing the asset provenance
- access - describing how the asset can be downloaded
- compute - describing how the asset can be computed upon
Each service is distinguished by the `DDO.service.type` attribute.
Each service has an `attributes` section where all the information related to the service is added. As mandatory content, the attributes section will have a `main` sub-section. This one is important because it must include all the mandatory information that a service has to provide.
A part of the `attributes.main` sub-section, other optional sub-sections can be added (like: `attributes.curation` or `attributes.extra`) depending on the service type.
Each service has an `cost` and `timeout` (in seconds) section describing the cost (how much datatokens needs to be transferred) and how long the sevice can be used after payment. A timeout of 0 represents no time limit.
Example:
```json
"service": [
{
"index": 0,
"type": "metadata",
"serviceEndpoint": "https://service/api/v1/metadata/assets/ddo/did:op:0ebed8226ada17fde24b6bf2b95d27f8f05fcce09139ff5cec31f6d81a7cd2ea",
"attributes": {
"main": {},
"additionalInformation": {},
"curation": {}
}
},
{
"index": 1,
"type": "access",
"serviceEndpoint": "http://localhost:8030/api/v1/brizo/services/consume",
"attributes": {
"main": {
"cost":"10",
"timeout":0
},
"additionalInformation": {}
}
},
{
"index": 2,
"type": "compute",
"serviceEndpoint": "http://localhost:8030/api/v1/brizo/services/compute",
"attributes": {
"main": {
"cost":"10",
"timeout":3600
},
"additionalInformation": {}
}
}
]
```
- You can find a [complete example of a DDO](ddo-example.json).
- You can find a complete reference of the asset metadata in [OEP-8](8).
- You can find a complete [real world example of a DDO](https://w3c-ccg.github.io/did-spec/#real-world-example) with extended services added, as part of the W3C DID spec.
#### Credentials
In order to support credentials based access. the following optional object is used:
```
"credentials":{
"allow":[
{
"type":"address",
"values":[
"0x123",
"0x456"
]
}
]
},
"deny":[
{
"type":"address",
"values":[
"0x2222",
"0x333"
]
}
]
}
```
where:
- "allow" - will control who can consume this asset. If array it's empty, means anyone can consume
- "deny" - if there is a match, consumption is denied
For future usage, we can extend that with different credentials types. Example:
```
{
"type":"credential3Box",
"values":[
"profile1",
"profile2"
]
}
```
#### DID Document Proof
Since V3, the metadata is stored on chain, so we don't need additional proofs, because we already have the transaction sender.
#### Length of a DID
The length of a DID must be compliant with the underlying storage layer and function calls. Given that decentralized virtual machines make use of contract languages such as Solidity and WASM, it is advised to fit the DID in structures such as `bytes32`.
It would be nice to store the `did:op:` prefix in those 32 bytes, but that means fewer than 32 bytes would be left for storing the rest (25 bytes since "did:op:" takes 7 bytes if using UTF-8). If the rest is a secure hash, then we need a 25-byte secure hash, but secure hashes typically have 28, 32 or more bytes, so that won't work.
Only the hash value _needs_ to be stored, not the `did:op:` prefix, because it should be clear from context that the value is an Ocean DID.
#### How to compute a DID
The DID (`id`) string begins with `did:op:` and is followed by a string representation of a bytes32.
In V3, the DID is based on the datatoken address.
## References
- [DID Spec from the W3C Credentials Community Group](https://w3c-ccg.github.io/did-spec/)
- [DID Spec from _Rebooting the Web of Trust_](https://github.com/WebOfTrustInfo/rebooting-the-web-of-trust-fall2016/blob/master/topics-and-advance-readings/did-spec-working-draft-03.md)
## Change Process
This document is governed by [OEP 2/COSS](../2/README.md).
## Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [BCP 14](https://tools.ietf.org/html/bcp14) \[[RFC2119](https://tools.ietf.org/html/rfc2119)\] \[[RFC8174](https://tools.ietf.org/html/rfc8174)\] when, and only when, they appear in all capitals, as shown here.

7
data/sidebars/concepts.yml
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@ -18,6 +18,13 @@
- title: Compute-to-Data Overview - title: Compute-to-Data Overview
link: /concepts/compute-to-data/ link: /concepts/compute-to-data/
- group: OEPs
items:
- title: DID
link: /concepts/oeps-did/
- title: Asset DDO
link: /concepts/oeps-asset-ddo/
- group: Contribute - group: Contribute
items: items:
- title: Ways to Contribute - title: Ways to Contribute