DID & DDO

Specification of decentralized identifiers for assets in Ocean Protocol using the DID & DDO standards.

v4.1.0

Overview

This document describes how Ocean assets follow the DID/DDO specification, such that Ocean assets can inherit DID/DDO benefits and enhance interoperability. DIDs and DDOs follow the specification defined by the World Wide Web Consortium (W3C).

Decentralized identifiers (DIDs) are a type of identifier that enable verifiable, decentralized digital identity. Each DID is associated with a unique entity, and DIDs may represent humans, objects, and more.

A DID Document (DDO) is a JSON blob that holds information about the DID. Given a DID, a resolver will return the DDO of that DID.

Rules for DID & DDO

An asset in Ocean represents a downloadable file, compute service, or similar. Each asset is a resource under the control of a publisher. The Ocean network itself does not store the actual resource (e.g. files).

An asset has a DID and DDO. The DDO should include metadata about the asset, and define access in at least one service. Only owners or delegated users can modify the DDO.

All DDOs are stored on-chain in encrypted form to be fully GDPR-compatible. A metadata cache like Aquarius can help in reading, decrypting, and searching through encrypted DDO data from the chain. Because the file URLs are encrypted on top of the full DDO encryption, returning unencrypted DDOs e.g. via an API is safe to do as the file URLs will still stay encrypted.

Publishing & Retrieving DDOs

The DDO is stored on-chain as part of the NFT contract and stored in encrypted form using the private key of the Provider. To resolve it, a metadata cache like Aquarius must query the provider to decrypt the DDO.

Here is the flow:

DDO flow
DDO flow

UML source
title DDO flow

User(Ocean library) -> User(Ocean library): Prepare DDO
User(Ocean library) -> Provider: encrypt DDO
Provider -> User(Ocean library): encryptedDDO
User(Ocean library) -> ERC721 contract: publish encryptedDDO
Aquarius <-> ERC721 contract: monitors ERC721 contract and gets MetdadataCreated Event (contains encryptedDDO)
Aquarius -> ERC721 contract: calls getMetaData()
Aquarius -> Provider: decrypt encryptedDDO, signed request using Aquarius's private key
Provider -> ERC721 contract: checks state using getMetaData()
Provider -> Provider: depending on metadataState (expired,retired) and aquarius address, validates the request
Provider -> Aquarius: DDO
Aquarius -> Aquarius : validate DDO
Aquarius -> Aquarius : cache DDO
Aquarius -> Aquarius : enhance cached DDO in response with additional infos like events & stats

DID

In Ocean, a DID is a string that looks like this:

did:op:0ebed8226ada17fde24b6bf2b95d27f8f05fcce09139ff5cec31f6d81a7cd2ea

The part after did:op: is the ERC721 contract address(in checksum format) and the chainId (expressed as a decimal) the asset has been published to:

const checksum = sha256(ERC721 contract address + chainId)
console.log(checksum)
// 0ebed8226ada17fde24b6bf2b95d27f8f05fcce09139ff5cec31f6d81a7cd2ea

It follows the generic DID scheme.

DDO

A DDO in Ocean has these required attributes:

AttributeTypeDescription
@contextArray of stringContexts used for validation.
idstringComputed as sha256(address of ERC721 contract + chainId).
versionstringVersion information in SemVer notation referring to this DDO spec version, like 4.1.0.
chainIdnumberStores chainId of the network the DDO was published to.
nftAddressstringNFT contract linked to this asset
metadataMetadataStores an object describing the asset.
servicesServicesStores an array of services defining access to the asset.
credentialsCredentialsDescribes the credentials needed to access a dataset in addition to the services definition.

Metadata

This object holds information describing the actual asset.

AttributeTypeRequiredDescription
createdISO date/time stringContains the date of the creation of the dataset content in ISO 8601 format preferably with timezone designators, e.g. 2000-10-31T01:30:00Z.
updatedISO date/time stringContains the date of last update of the dataset content in ISO 8601 format preferably with timezone designators, e.g. 2000-10-31T01:30:00Z.
descriptionstringDetails of what the resource is. For a dataset, this attribute explains what the data represents and what it can be used for.
copyrightHolderstringThe party holding the legal copyright. Empty by default.
namestringDescriptive name or title of the asset.
typestringAsset type. Includes "dataset" (e.g. csv file), "algorithm" (e.g. Python script). Each type needs a different subset of metadata attributes.
authorstringName of the entity generating this data (e.g. Tfl, Disney Corp, etc.).
licensestringShort 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”.
linksArray of stringMapping of URL strings for data samples, or links to find out more information. Links may be to either a URL or another asset.
contentLanguagestringThe language of the content. Use one of the language codes from the IETF BCP 47 standard
tagsArray of stringArray of keywords or tags used to describe this content. Empty by default.
categoriesArray of stringArray of categories associated to the asset. Note: recommended to use tags instead of this.
additionalInformationObjectStores additional information, this is customizable by publisher
algorithmAlgorithm Metadata (for algorithm assets only)Information about asset of typealgorithm

Example:

{
  "metadata": {
    "created": "2020-11-15T12:27:48Z",
    "updated": "2021-05-17T21:58:02Z",
    "description": "Sample description",
    "name": "Sample asset",
    "type": "dataset",
    "author": "OPF",
    "license": "https://market.oceanprotocol.com/terms"
  }
}

Algorithm Metadata

An asset of type algorithm has additional attributes under metadata.algorithm, describing the algorithm and the Docker environment it is supposed to be run under.

AttributeTypeRequiredDescription
languagestringLanguage used to implement the software.
versionstringVersion of the software preferably in SemVer notation. E.g. 1.0.0.
consumerParametersConsumer ParametersAn object that defines required consumer input before running the algorithm
containercontainerObject describing the Docker container image. See below

The container object has the following attributes defining the Docker image for running the algorithm:

AttributeTypeRequiredDescription
entrypointstringThe command to execute, or script to run inside the Docker image.
imagestringName of the Docker image.
tagstringTag of the Docker image.
checksumstringDigest of the Docker image. (ie: sha256:xxxxx)
{
  "metadata": {
    "created": "2020-11-15T12:27:48Z",
    "updated": "2021-05-17T21:58:02Z",
    "description": "Sample description",
    "name": "Sample algorithm asset",
    "type": "algorithm",
    "author": "OPF",
    "license": "https://market.oceanprotocol.com/terms",
    "algorithm": {
      "language": "Node.js",
      "version": "1.0.0",
      "container": {
        "entrypoint": "node $ALGO",
        "image": "ubuntu",
        "tag": "latest",
        "checksum": "sha256:44e10daa6637893f4276bb8d7301eb35306ece50f61ca34dcab550"
      },
      "consumerParameters": {}
    }
  }
}

Services

Services define the access for an asset, and each service is represented by its respective datatoken.

An asset should have at least one service to be actually accessible, and can have as many services which make sense for a specific use case.

AttributeTypeRequiredDescription
idstringUnique ID
typestringType of service (access, compute, wss, etc.
namestringService friendly name
descriptionstringService description
datatokenAddressstringDatatoken address
serviceEndpointstringProvider URL (schema + host)
filesFilesEncrypted file URLs.
timeoutnumberDescribing how long the service can be used after consumption is initiated. A timeout of 0 represents no time limit. Expressed in seconds.
computeCompute (for compute assets only)If service is of typecompute, holds information about the compute-related privacy settings & resources.
consumerParametersConsumer ParametersAn object the defines required consumer input before consuming the asset
additionalInformationObjectStores additional information, this is customizable by publisher

Files

The files field is returned as a string which holds the encrypted file URLs.

Example:

{
  "files": "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"
}

During the publish process, file URLs must be encrypted with a respective Provider API call before storing the DDO on-chain. For this, you need to send the following object to Provider:

{
  "datatokenAddress":"0x1",
  "nftAddress": "0x2",
  "files": [
    ...
  ]
}

where “files” contains one or more storage objects.

Type of objects supported :

TypeDescriptionExample
urlStatic URL. Contains url and HTTP method
[
  {
    "type": "url",
    "url": "https://url.com/file1.csv",
    "method": "GET",
    "headers":
      [
       {"Authorization": "Bearer 123"}, 
       {"APIKEY": "124"},
      ]
  }
]

First class integrations supported in the future :

TypeDescriptionExample
ipfsIPFS files
[
  {
    "type": "ipfs",
    "hash": "XXX"
  }
]
filecoinFilecoin storage 
arwaveArwave 
storjStorj 
sqlSql connection, dataset is generated by a query 

A service can contain multiple files, using multiple storage types.

Example:

{
  "datatokenAddress":"0x1",
  "nftAddress": "0x2",
  "files": [
    {
      "type": "url",
      "url": "https://url.com/file1.csv",
      "method": "GET"
    },
    {
      "type": "ipfs",
      "hash": "XXXX"
    }
  ]
}

To get information about the files after encryption, the /fileinfo endpoint of Provider returns based on a passed DID an array of file metadata (based on the file type):

[
  {
    "type": "url",
    "contentLength": 100,
    "contentType": "application/json"
  },
  {
    "type": "ipfs",
    "contentLength": 130,
    "contentType": "application/text"
  }
]

This only concerns metadata about a file, but never the file URLs. The only way to decrypt them is to exchange at least 1 datatoken based on the respective service pricing scheme.

Compute Options

An asset with a service of type compute has the following additional attributes under the compute object. This object is required if the asset is of type compute, but can be omitted for type of access.

allowRawAlgorithm
TypeRequiredDescription
booleanIf true, any passed raw text will be allowed to run. Useful for an algorithm drag & drop use case, but increases risk of data escape through malicious user input. Should be false by default in all implementations.
allowNetworkAccess
TypeRequiredDescription
booleanIf true, the algorithm job will have network access.
publisherTrustedAlgorithmPublishers
TypeRequiredDescription
Array of stringIf not defined, then any published algorithm is allowed. If empty array, then no algorithm is allowed. If not empty any algo published by the defined publishers is allowed.
publisherTrustedAlgorithms
TypeRequiredDescription
Array of publisherTrustedAlgorithmsIf not defined, then any published algorithm is allowed. If empty array, then no algorithm is allowed. Otherwise only the algorithms defined in the array are allowed. (see below).

The publisherTrustedAlgorithms is an array of objects with the following structure:

AttributeTypeRequiredDescription
didstringThe DID of the algorithm which is trusted by the publisher.
filesChecksumstringHash of algorithm’s files (as string).
containerSectionChecksumstringHash of algorithm’s image details (as string).

To produce filesChecksum, call the Provider FileInfoEndpoint with parameter withChecksum = True. If algorithm has multiple files, filesChecksum is a concatenated string of all files checksums (ie: checksumFile1+checksumFile2 , etc)

To produce containerSectionChecksum:

sha256(algorithm_ddo.metadata.algorithm.container.entrypoint + algorithm_ddo.metadata.algorithm.container.checksum)

Example:

{
  "services": [
    {
      "id": "1",
      "type": "access",
      "files": "0x044736da6dae39889ff570c34540f24e5e084f...",
      "name": "Download service",
      "description": "Download service",
      "datatokenAddress": "0x123",
      "serviceEndpoint": "https://myprovider.com",
      "timeout": 0
    },
    {
      "id": "2",
      "type": "compute",
      "files": "0x6dd05e0edb460623c843a263291ebe757c1eb3...",
      "name": "Compute service",
      "description": "Compute service",
      "datatokenAddress": "0x124",
      "serviceEndpoint": "https://myprovider.com",
      "timeout": 0,
      "compute": {
        "allowRawAlgorithm": false,
        "allowNetworkAccess": true,
        "publisherTrustedAlgorithmPublishers": ["0x234", "0x235"],
        "publisherTrustedAlgorithms": [
          {
            "did": "did:op:123",
            "filesChecksum": "100",
            "containerSectionChecksum": "200"
          },
          {
            "did": "did:op:124",
            "filesChecksum": "110",
            "containerSectionChecksum": "210"
          }
        ]
      }
    }
  ]
}

Consumer Parameters

Sometimes, the asset needs additional input data before downloading or running a Compute-to-Data job. Examples:

  • The publisher needs to know the sampling interval before the buyer downloads it. Suppose the dataset URL is https://example.com/mydata. The publisher defines a field called sampling and asks the buyer to enter a value. This parameter is then added to the URL of the published dataset as query parameters: https://example.com/mydata?sampling=10.
  • An algorithm that needs to know the number of iterations it should perform. In this case, the algorithm publisher defines a field called iterations. The buyer needs to enter a value for the iterations parameter. Later, this value is stored in a specific location in the Compute-to-Data pod for the algorithm to read and use it.

The consumerParameters is an array of objects. Each object defines a field and has the following structure:

AttributeTypeRequiredDescription
namestringThe parameter name (this is sent as HTTP param or key towards algo)
typestringThe field type (text, number, boolean, select)
labelstringThe field label which is displayed
requiredbooleanIf customer input for this field is mandatory.
descriptionstringThe field description.
defaultstring, number, or booleanThe field default value. For select types, string key of default option.
optionsArray of optionFor select types, a list of options.

Each option is an object containing a single key:value pair where the key is the option name, and the value is the option value.

Example:

[
  {
    "name": "hometown",
    "type": "text",
    "label": "Hometown",
    "required": true,
    "description": "What is your hometown?",
    "default": "Nowhere"
  },
  {
    "name":"age",
    "type": "number",
    "label": "Age",
    "required": false,
    "description":"Please fill your age",
    "default": 0
  },
  {
    "name":"developer",
    "type": "boolean",
    "label": "Developer",
    "required": false,
    "description":"Are you a developer?",
    "default": false
  },
  {
    "name":"languagePreference",
    "type": "select",
    "label": "Language",
    "required": false,
    "description": "Do you like NodeJs or Python",
    "default": "nodejs",
    "options": [
      {
        "nodejs" : "I love NodeJs"
      },
      {
        "python" : "I love Python"
      }
    ]
  }
]

Algorithms will have access to a JSON file located at /data/inputs/algoCustomData.json, which contains the keys/values for input data required. Example:

{
  "hometown": "São Paulo",
  "age": 10,
  "developer": true,
  "languagePreference": "nodejs"
}

Credentials

By default, a consumer can access a resource if they have 1 datatoken. Credentials allow the publisher to optionally specify more fine-grained permissions.

Consider a medical data use case, where only a credentialed EU researcher can legally access a given dataset. Ocean supports this as follows: a consumer can only access the resource if they have 1 datatoken and one of the specified "allow" credentials.

This is like going to an R-rated movie, where you can only get in if you show both your movie ticket (datatoken) and some identification showing you’re old enough (credential).

Only credentials that can be proven are supported. This includes Ethereum public addresses, and in the future W3C Verifiable Credentials and more.

Ocean also supports "deny" credentials: if a consumer has any of these credentials, they can not access the resource.

Here’s an example object with both "allow" and "deny" entries:

{
  "credentials": {
    "allow": [
      {
        "type": "address",
        "values": ["0x123", "0x456"]
      }
    ],
    "deny": [
      {
        "type": "address",
        "values": ["0x2222", "0x333"]
      }
    ]
  }
}

DDO Checksum

In order to ensure the integrity of the DDO, a checksum is computed for each DDO:

const checksum = sha256(JSON.stringify(ddo))

The checksum hash is used when publishing/updating metadata using the setMetaData function in the ERC721 contract, and is stored in the event generated by the ERC721 contract:

event MetadataCreated(
  address indexed createdBy,
  uint8 state,
  string decryptorUrl,
  bytes flags,
  bytes data,
  bytes metaDataHash,
  uint256 timestamp,
  uint256 blockNumber
);

event MetadataUpdated(
  address indexed updatedBy,
  uint8 state,
  string decryptorUrl,
  bytes flags,
  bytes data,
  bytes metaDataHash,
  uint256 timestamp,
  uint256 blockNumber
);

Aquarius should always verify the checksum after data is decrypted via a Provider API call.

State

Each asset has a state, which is held by the NFT contract. The possible states are:

StateDescription
0Active.
1End-of-life.
2Deprecated (by another asset).
3Revoked by publisher.
4Ordering is temporary disabled.

Aquarius Enhanced DDO Response

The following fields are added by Aquarius in its DDO response for convenience reasons, where an asset returned by Aquarius inherits the DDO fields stored on-chain.

These additional fields are never stored on-chain, and are never taken into consideration when hashing the DDO.

NFT

The nft object contains information about the ERC721 NFT contract which represents the intellectual property of the publisher.

AttributeTypeDescription
addressstringContract address of the deployed ERC721 NFT contract.
namestringName of NFT set in contract.
symbolstringSymbol of NFT set in contract.
ownerstringETH account address of the NFT owner.
statenumberState of the asset reflecting the NFT contract value. See State
createdISO date/time stringContains the date of NFT creation.
tokenURIstringtokenURI

Example:

{
  "nft": {
    "address": "0x000000",
    "name": "Ocean Protocol Asset v4",
    "symbol": "OCEAN-A-v4",
    "owner": "0x0000000",
    "state": 0,
    "created": "2000-10-31T01:30:00Z"
  }
}

Datatokens

The datatokens array contains information about the ERC20 datatokens attached to asset services.

AttributeTypeDescription
addressstringContract address of the deployed ERC20 contract.
namestringName of NFT set in contract.
symbolstringSymbol of NFT set in contract.
serviceIdstringID of the service the datatoken is attached to.

Example:

{
  "datatokens": [
    {
      "address": "0x000000",
      "name": "Datatoken 1",
      "symbol": "DT-1",
      "serviceId": "1"
    },
    {
      "address": "0x000001",
      "name": "Datatoken 2",
      "symbol": "DT-2",
      "serviceId": "2"
    }
  ]
}

Event

The event section contains information about the last transaction that created or updated the DDO.

Example:

{
  "event": {
    "tx": "0x8d127de58509be5dfac600792ad24cc9164921571d168bff2f123c7f1cb4b11c",
    "block": 12831214,
    "from": "0xAcca11dbeD4F863Bb3bC2336D3CE5BAC52aa1f83",
    "contract": "0x1a4b70d8c9DcA47cD6D0Fb3c52BB8634CA1C0Fdf",
    "datetime": "2000-10-31T01:30:00"
  }
}

Purgatory

Contains information about an asset’s purgatory status defined in list-purgatory. Marketplace interfaces are encouraged to prevent certain user actions like adding liquidity on assets in purgatory.

AttributeTypeDescription
statebooleanIf true, asset is in purgatory.
reasonstringIf asset is in purgatory, contains the reason for being there as defined in list-purgatory.

Example:

{
  "purgatory": {
    "state": true,
    "reason": "Copyright violation"
  }
}
{
  "purgatory": {
    "state": false
  }
}

Statistics

The stats section contains different statistics fields.

AttributeTypeDescription
ordersnumberHow often an asset was ordered, meaning how often it was either downloaded or used as part of a compute job.

Example:

{
  "stats": {
    "orders": 4
  }
}

Full Enhanced DDO Example

{
  "@context": ["https://w3id.org/did/v1"],
  "id": "did:op:ACce67694eD2848dd683c651Dab7Af823b7dd123",
  "version": "4.1.0",
  "chainId": 1,
  "nftAddress": "0x123",
  "metadata": {
    "created": "2020-11-15T12:27:48Z",
    "updated": "2021-05-17T21:58:02Z",
    "description": "Sample description",
    "name": "Sample asset",
    "type": "dataset",
    "author": "OPF",
    "license": "https://market.oceanprotocol.com/terms"
  },
  "services": [
    {
      "id": "1",
      "type": "access",
      "files": "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",
      "name": "Download service",
      "description": "Download service",
      "datatokenAddress": "0x123",
      "serviceEndpoint": "https://myprovider.com",
      "timeout": 0,
      "consumerParameters": [
        {
          "name": "surname",
          "type": "text",
          "label": "Name",
          "required": true,
          "default": "NoName",
          "description": "Please fill your name"
        },
        {
          "name": "age",
          "type": "number",
          "label": "Age",
          "required": false,
          "default": 0,
          "description": "Please fill your age"
        }
      ]
    },
    {
      "id": "2",
      "type": "compute",
      "files": "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",
      "name": "Compute service",
      "description": "Compute service",
      "datatokenAddress": "0x124",
      "serviceEndpoint": "https://myprovider.com",
      "timeout": 3600,
      "compute": {
        "allowRawAlgorithm": false,
        "allowNetworkAccess": true,
        "publisherTrustedAlgorithmPublishers": ["0x234", "0x235"],
        "publisherTrustedAlgorithms": [
          {
            "did": "did:op:123",
            "filesChecksum": "100",
            "containerSectionChecksum": "200"
          },
          {
            "did": "did:op:124",
            "filesChecksum": "110",
            "containerSectionChecksum": "210"
          }
        ]
      }
    }
  ],
  "credentials": {
    "allow": [
      {
        "type": "address",
        "values": ["0x123", "0x456"]
      }
    ],
    "deny": [
      {
        "type": "address",
        "values": ["0x2222", "0x333"]
      }
    ]
  },

  "nft": {
    "address": "0x123",
    "name": "Ocean Protocol Asset v4",
    "symbol": "OCEAN-A-v4",
    "owner": "0x0000000",
    "state": 0,
    "created": "2000-10-31T01:30:00",
    "tokenURI": "xxx"
  },

  "datatokens": [
    {
      "address": "0x000000",
      "name": "Datatoken 1",
      "symbol": "DT-1",
      "serviceId": "1"
    },
    {
      "address": "0x000001",
      "name": "Datatoken 2",
      "symbol": "DT-2",
      "serviceId": "2"
    }
  ],

  "event": {
    "tx": "0x8d127de58509be5dfac600792ad24cc9164921571d168bff2f123c7f1cb4b11c",
    "block": 12831214,
    "from": "0xAcca11dbeD4F863Bb3bC2336D3CE5BAC52aa1f83",
    "contract": "0x1a4b70d8c9DcA47cD6D0Fb3c52BB8634CA1C0Fdf",
    "datetime": "2000-10-31T01:30:00"
  },

  "purgatory": {
    "state": false
  },

  "stats": {
    "orders": 4
  }
}