Digital Twin¶

Class Name	DigitalTwin
Extends	Logger
Source	digital-twin.ts
Examples	digital-twin.spec.ts

TL;DR: usage examples and a data flow can be found here.

A DigitalTwin is a wrapper, that holds data or references to data. This data can be

a Container - This is the most common use case, actual data is stored in the container and the DigitalTwin merely holds a reference to the container.
an DigitalTwin - DigitalTwins can be linked together, so an entry can be another DigitalTwin, which allows to navigate through twins to retrieve data properties from linked twins, see getEntry
an account address / a contract address
bytes32 hashes (e.g. file hashes)

constructor¶

new DigitalTwin(options, config);

Create new DigitalTwin instance. This will not create a smart contract contract but is used to load existing digital twins. To create a new contract, use the static create function.

Parameters¶

options - DigitalTwinOptions: runtime-like object with required modules
- contractLoader - ContractLoader: ContractLoader instance
- cryptoProvider - CryptoProvider: CryptoProvider instance
- dataContract - DataContract: DataContract instance
- description - Description: Description instance
- executor - Executor: Executor instance
- log - Function (optional): function to use for logging: (message, level) => {...}
- logLevel - LogLevel (optional): messages with this level will be logged with log
- logLog - LogLogInterface (optional): container for collecting log messages
- logLogLevel - LogLevel (optional): messages with this level will be pushed to logLog
- nameResolver - NameResolver: NameResolver instance
- profile - Profile: Profile instance
- rightsAndRoles - RightsAndRoles: RightsAndRoles instance
- sharing - Sharing: Sharing instance
- verifications - Verifications: Verifications instance
- web3 - Web3: Web3 instance
config - DigitalTwinConfig: digital twin related config
- accountId - string: account id of user, that interacts with digital twin
- containerConfig - ContainerConfig: address of a DigitalTwin instance, can be ENS or contract address
- address - string (optional): address of an DigitalTwin instance, can be ENS or contract address
- description - string: description has to be passed to .create to apply it to to contract
- factoryAddress - string (optional): factory address can be passed to .create for customer digital twin factory

Returns¶

DigitalTwin instance

Example¶

const digitalTwin = new DigitalTwin(
  runtime,
  {
    accountId: '0x0000000000000000000000000000000000000000',
    address: 'sample-digital-twin.somewhere.evan',
  },
);

= Creating Digital Identities =¶

create¶

DigitalTwin.create(runtime, config);

Create digital twin contract.

Note, that this function is static. It is used on the DigitalTwin class object and returns a DigitalTwin class instance.

The options argument has the same structure as the options object that is passed to the constructor as it is used for the new DigitalTwin instance. The config argument requires a proper value for the property description.

Parameters¶

options - ContainerOptions: runtime-like object with required modules
- contractLoader - ContractLoader: ContractLoader instance
- cryptoProvider - CryptoProvider: CryptoProvider instance
- dataContract - DataContract: DataContract instance
- description - Description: Description instance
- executor - Executor: Executor instance
- nameResolver - NameResolver: NameResolver instance
- rightsAndRoles - RightsAndRoles: RightsAndRoles instance
- sharing - Sharing: Sharing instance
- verifications - Verifications: Verifications instance
- web3 - Web3: Web3 instance
- log - Function (optional): function to use for logging: (message, level) => {...}
- logLevel - LogLevel (optional): messages with this level will be logged with log
- logLog - LogLogInterface (optional): container for collecting log messages
- logLogLevel - LogLevel (optional): messages with this level will be pushed to logLog
config - DigitalTwinConfig: digital twin related config
- accountId - string: account id of user, that interacts with digital twin
- containerConfig - ContainerConfig: config, that will be used, when containers are created
- address - string (optional): ENS address used for digital twin
- description - string: description has to be passed to .create to apply it to to contract
- factoryAddress - string (optional): factory address can be passed to .create for customer digital twin factory

Returns¶

Promise returns DigitalTwin: new instance bound to new DigitalTwin

Example¶

const digitalTwin = await DigitalTwin.create(options, config);
console.log(await digitalTwin.getContractAddress());
// Output:
// 0x0000000000000000000000000000000000001234

= Container =¶

createContainers¶

digitalTwin.createContainers(containers);

Create new Container instances and add them as entry to twin.

When a container entry fetched with getEntry or getEntry, the value will become a Container instance and can be used as such.

Parameters¶

containers - { [id: string]: Partial<ContainerConfig> }: object with containers to create, name is used as entry name in twin

Returns¶

Promise returns { [id: string]: Container }: map with Container instances

Example¶

const containers = await twin.createContainers({
  entry1: { template: 'metadata' },
  entry2: { template: 'metadata' },
});

= Entries =¶

setEntry¶

digitalTwin.setEntry(name, value, entryType);

Set entry in index contract; entries are unique, setting the same name a second time will overwrite the first value.

Parameters¶

name - string: entry name
value - string: value to set
entryType - DigitalTwinType: type of given value

Returns¶

Promise returns void: resolved when done

Example¶

await digitalTwin.setEntry('myId', accountId, DigitalTwinEntryType.AccountId);
console.log((await digitalTwin.getEntry('myId')).value);
// Output:
// 0x0000000000000000000000000000000000000001

setEntries¶

digitalTwin.setEntries(arguments);

Set multiple entries at index contract.

Parameters¶

entries - {[id: string]: DigitalTwinIndexEntry}: entries to set

Returns¶

Promise returns void: resolved when done

Example¶

const sampleContractId = '0x00000000000000000000000000000000c0274ac7';
await digitalTwin.setEntries({
  'account':  { value: accountId, entryType: DigitalTwinEntryType.AccountId },
  'contract':  { value: sampleContractId, entryType: DigitalTwinEntryType.GenericContract },
});

const result = (await digitalTwin.getEntries()).map(entry => value);
console.log(result.account.value);
// Output:
// 0x0000000000000000000000000000000000000001
console.log(result.contract.value);
// Output:
// 0x00000000000000000000000000000000c0274ac7

getEntry¶

digitalTwin.getEntry(name);

Get single entry from index contract.

When this twin has other twins as its entries, properties from those can be selected by building a path of properties.

For example a twin called car may have a link to another twin under the name tire. The twin tire has an entry called metadata. It is possible to retrieve this entry from the twin car with:

const tireMetadata = await car.getEntry('tire/metadata');

Parameters¶

name - string: entry name or path to data in linked twin

Returns¶

Promise returns DigitalTwinIndexEntry: entry object

Example¶

await digitalTwin.setEntry('myId', accountId, DigitalTwinEntryType.AccountId);
console.log((await digitalTwin.getEntry('myId')).value);
// Output:
// 0x0000000000000000000000000000000000000001

getEntries¶

digitalTwin.getEntries();

Get all entries from index contract.

Returns¶

Promise returns {[id: string]: DigitalTwinIndexEntry}: key-value map with all entries

Example¶

const sampleContractId = '0x00000000000000000000000000000000c0274ac7';
await digitalTwin.setEntries({
  'account':  { value: accountId, entryType: DigitalTwinEntryType.AccountId },
  'contract':  { value: sampleContractId, entryType: DigitalTwinEntryType.GenericContract },
});

const result = (await digitalTwin.getEntries()).map(entry => value);
console.log(result.account.value);
// Output:
// 0x0000000000000000000000000000000000000001
console.log(result.contract.value);
// Output:
// 0x00000000000000000000000000000000c0274ac7

= Verifications =¶

addVerifications¶

digitalTwin.addVerifications(verifications);

Add verifications to this twin; this will also add verifications to contract description.

If the calling account is the owner of the identity of the digital twin

the description will is automatically updated with tags for verifications
verifications issued with this function will be accepted automatically

See interface DigitalTwinVerificationEntry for input data format.

Parameters¶

verifications - DigitalTwinVerificationEntry[]: list of verifications to add

Returns¶

Promise returns void: resolved when done

Example¶

await digitalTwin.addVerifications([{ topic: 'exampleVerification' }]);

getVerifications¶

digitalTwin.getVerifications();

Gets verifications from description and fetches list of verifications for each of them.

See Verifications documentation for details on output data format.

Returns¶

Promise returns any: list of verification lists from Verifications, getVerifications

Example¶

await digitalTwin.addVerifications([{ topic: 'exampleVerification' }]);
const verifications = await digitalTwin.getVerifications());

= Descriptions =¶

getDescription¶

digitalTwin.getDescription();

Returns description from digital twin.

Returns¶

Promise returns any: public part of the description

Example¶

const description = await container.getDescription();
console.dir(description);
// Output:
// { name: 'test twin',
//   description: 'twin from test run',
//   author: 'evan GmbH',
//   version: '0.1.0',
//   dbcpVersion: 2,
//   tags: [ 'evan-digital-twin' ],
//   identity:
//    '0x1a496043385fec8d52f61e2b700413f8e12eb6e7e11649f80c8f4716c1063d06' }

setDescription¶

digitalTwin.setDescription(description);

Write given description to digital twins DBCP.

Parameters¶

description - any: description (public part)

Returns¶

Promise returns void: resolved when done

Example¶

// get current description
const description = await digitalTwin.getDescription();
console.dir(description);
// Output:
// { name: 'test twin',
//   description: 'twin from test run',
//   author: 'evan GmbH',
//   version: '0.1.0',
//   dbcpVersion: 2,
//   tags: [ 'evan-digital-twin' ],
//   identity:
//    '0x1a496043385fec8d52f61e2b700413f8e12eb6e7e11649f80c8f4716c1063d06' }

// update description
description.version = '0.1.1';
await digitalTwin.setDescription(description);

// fetch again
console.dir(await digitalTwin.getDescription());
// Output:
// { name: 'test twin',
//   description: 'twin from test run',
//   author: 'evan GmbH',
//   version: '0.1.1',
//   dbcpVersion: 2,
//   tags: [ 'evan-digital-twin' ],
//   identity:
//    '0x1a496043385fec8d52f61e2b700413f8e12eb6e7e11649f80c8f4716c1063d06' }

= Profile =¶

addAsFavorite¶

digitalTwin.addAsFavorite();

Add the digital twin with given address to profile.

Returns¶

Promise returns void: resolved when done

Example¶

const digitalTwin = new DigitalTwin(options.config);
if (await digitalTwin.isFavorite()) {
  console.log('I know this digital twin!');
} else {
  await digitalTwin.addToFavorites();
  console.log('bookmarked digital twin');
}

getFavorites¶

DigitalTwin.getFavorites();

Gets bookmarked twins from profile.

Note, that this function is called on the Class DigitalTwin and not on an instance of it.

Parameters¶

options - ContainerOptions: runtime-like object with required modules
- contractLoader - ContractLoader: ContractLoader instance
- cryptoProvider - CryptoProvider: CryptoProvider instance
- dataContract - DataContract: DataContract instance
- description - Description: Description instance
- executor - Executor: Executor instance
- nameResolver - NameResolver: NameResolver instance
- rightsAndRoles - RightsAndRoles: RightsAndRoles instance
- sharing - Sharing: Sharing instance
- verifications - Verifications: Verifications instance
- web3 - Web3: Web3 instance
- log - Function (optional): function to use for logging: (message, level) => {...}
- logLevel - LogLevel (optional): messages with this level will be logged with log
- logLog - LogLogInterface (optional): container for collecting log messages
- logLogLevel - LogLevel (optional): messages with this level will be pushed to logLog

Returns¶

Promise returns void: resolved when done

Example¶

const favorites = await DigitalTwin.getFavorites(options);
console.dir(favorites);
// Output:
// [
//  'example.somewhere.evan',
//  'another.example.somewhere.else.evan',
//  '0x0000000000000000000000000000000000001234'
// ]

isFavorite¶

digitalTwin.isFavorite();

Check if this digital twin is bookmarked in profile.

Returns¶

Promise returns boolean: true if bookmarked

Example¶

const digitalTwin = new DigitalTwin(options.config);
if (await digitalTwin.isFavorite()) {
  console.log('I know this digital twin!');
} else {
  await digitalTwin.addToFavorites();
  console.log('bookmarked digital twin');
}

removeFromFavorites¶

digitalTwin.removeFromFavorites();

Removes the current twin from the favorites in profile.

Returns¶

Promise returns void: resolved when done

Example¶

const digitalTwin = new DigitalTwin(options.config);
if (await digitalTwin.isFavorite()) {
  await digitalTwin.removeFromFavorites();
  console.log('removed digital twin from favorites');
}

= Utilities =¶

getValidity¶

DigitalTwin.getValidity(options, ensAddress);

Check if a valid contract is located under the specified address, which allows to check for twins before actually loading them.

Return value properties have the following meaning:

valid: true if contract could not be found or if it doesn’t have the tag “evan-digital-twin”
exists: true if a contract address could be found at given ENS address
error: an error object, if one of the other properties is false

Note, that this function is called on the Class DigitalTwin and not on an instance of it.

Parameters¶

options - DigitalTwinOptions: twin runtime options
- contractLoader - ContractLoader: ContractLoader instance
- cryptoProvider - CryptoProvider: CryptoProvider instance
- dataContract - DataContract: DataContract instance
- description - Description: Description instance
- executor - Executor: Executor instance
- nameResolver - NameResolver: NameResolver instance
- rightsAndRoles - RightsAndRoles: RightsAndRoles instance
- sharing - Sharing: Sharing instance
- verifications - Verifications: Verifications instance
- web3 - Web3: Web3 instance
- log - Function (optional): function to use for logging: (message, level) => {...}
- logLevel - LogLevel (optional): messages with this level will be logged with log
- logLog - LogLogInterface (optional): container for collecting log messages
- logLogLevel - LogLevel (optional): messages with this level will be pushed to logLog
ensAddress - string: ens address that should be checked

Returns¶

Promise returns { valid: boolean, exists: boolean, error: Error }: resolved when done

Example¶

const { valid } = await DigitalTwin.getValidity(runtime, address);
if (!valid) {
  throw new Error(`no valid digital twin found at "${address}"`);
}

ensureContract¶

digitalTwin.ensureContract();

Check if digital twin contract already has been loaded, load from address / ENS if required. Throws if contract could not be loaded.

This function is more commonly used for internal checks in the DigitalTwin module. For checking, if a given address can be used, it is recommended to use getValidity.

Returns¶

Promise returns void: resolved when done

Example¶

let digitalTwin;
try {
  digitalTwin = new DigitalTwin(options, config);
  await digitalTwin.ensureContract();
  // use digital twin
} catch (ex) {
  console.error(`could use digital twin; ${ex.message || ex}`);
}

getContractAddress¶

digitalTwin.getContractAddress();

Get contract address of underlying DigitalTwin.

Returns¶

Promise returns string: contract address

Example¶

const digitalTwin = new DigitalTwin(options, config);
console.log(await digitalTwin.getContractAddress());
// Output:
// 0x000000000000000000000000000000001d327171

Additional Components¶

Public Properties¶

defaultDescription (static)¶

Default description used when no specific description is given to .create.

console.dir(DigitalTwin.defaultDescription);
// Output:
// {
//   name: 'Digital Identity',
//   description: 'Digital Identity Contract',
//   author: '',
//   version: '0.1.0',
//   dbcpVersion: 2
// }

Enums¶

DigitalTwinEntryType¶

possible entry types for entries in index

AccountId
Container
FileHash
GenericContract
Hash
DigitalTwin

Interfaces¶

DigitalTwinConfig¶

config for digital twin

accountId - string: account id of user, that interacts with digital twin
containerConfig - ContainerConfig: address of a DigitalTwin instance, can be ENS or contract address
address - string (optional): address of an DigitalTwin instance, can be ENS or contract address
description - string (optional): description has to be passed to .create to apply it to to contract
factoryAddress - string (optional): factory address can be passed to .create for customer digital twin factory

DigitalTwinIndexEntry¶

container for digital twin entry values

entryType - DigitalTwinEntryType (optional): type of entry in index
raw - any (optional): raw value (bytes32 hash)
value - any (optional): decrypted/loaded value

DigitalTwinVerificationEntry¶

data for verifications for digital twins

topic - string: name of the verification (full path)
descriptionDomain - string (optional): domain of the verification, this is a subdomain under ‘verifications.evan’, so passing ‘example’ will link verifications
disableSubVerifications - boolean (optional): if true, verifications created under this path are invalid, defaults to false
expirationDate - number (optional): expiration date, for the verification, defaults to 0 (does not expire)
verificationValue - any (optional): json object which will be stored in the verification