GLO specification

The Generic Ledger Operation (GLO) specification defines a standard, language-agnostic interface to define operations that can be performed on any Distributed Ledger Technology (DLT).

Versions

The GLO specification is subject to change to adapt to the constantly changing nature of ledger technologies. For this reason, the structure is versioned using Semantic Versioning.

The current version is 0.1.0.

GLO structure

GLOs are represented as JSON objects. The following is a list of the fields that are common to all GLOs:

Field	Type	Description
version	string	Required Version of the GLO structure.
type	GLO Type enum	Required Type of operation to be performed on a given DLT network.
options	GLO Options object	Required Ledger-agnostic options of the operation.
meta	GLO Meta	Ledger-specific options of the operation.

Example:

{ 
    "version": "0.1.0", 
    "type": "transfer", 
    "options": { 
        "recipient": { 
            "lookup_service": { 
                "type": "ledger", 
                "value": "ethereum" 
            }, 
            "resource": "0xfea8e07b145bb611a4b5ab5c015f3cc3644c083a"
        }, 
        "amount": 0 
    } 
}

Schemas

GLO Type enum

List of supported GLO types:

• transfer: Transfer of native currency funds.
• contract_call: Method call of a deployed smart contract.
• contract_deploy: Deployment of a smart contract.

GLO Options object

The body of the operation is generic for all ledger technologies MARCO supports. This object structure varies depending on the type of operation.

transfer options

An object representing the transfer GLO options.

Field	Type	Description
recipient	Resource Locator object	Required. Resource locator of the recipient of the funds.
amount	string or number	Required. Amount of native currency to transfer to recipient.

Example:

{
    "recipient": {
        "lookup_service": {
            "type": "ledger",
            "value": "ethereum"
        },
        "resource": "0xfea8e07b145bb611a4b5ab5c015f3cc3644c083a"
    },
    "amount": 0
}

contract_call options

An object representing the contract_call GLO options.

Field	Type	Description
contract_instance	Resource Locator object	Required. Smart contract instance locator.
method_name	string	Required. Method of the contract instance to be called.
args	List of strings	List of arguments passed to the method in the order defined.

Example:

{
    "contract_instance": {
        "lookup_service": {
            "type": "ledger",
            "value": "ethereum"
        },
        "resource": "0x8b0b7b8c7c7a4b2b4ab15c6d62a01a019b44b827"
    },
    "method_name": "set",
    "args": ["0x1234567890123456789012345678901234567890", "0x1234567890123456789012345678901234567890"]
}

contract_deploy options

An object representing the contract_deploy GLO options.

Field	Type	Description
contract_source	Resource Locator object	Required. Smart contract source locator.
args	List of strings	Arguments used to initialise the contract.

Example:

{
    "contract_source": {
        "lookup_service": {
            "type": "marco",
            "value": "marco"
        },
        "resource": "SCT-oNO0BYzLnho:0.0.1"
    },
    "args": ["Hello World!"]
}

GLO Meta object

An object that is used to specify native ledger-specific options for an operation. Its content varies depending on the DLT being used.

For example, when using the Ethereum ledger, the native_transaction_content field can be used to specify options specific to Ethereum transactions, such as the gasPrice and gasLimit.

Example:

{
  "ledger": {
    "ethereum": {
      "version": "0.0.1",
      "native_transaction_content": {
        "gasPrice": "0",
        "gasLimit": "0"
      }
    }
  }
}

If there is a conflict between the GLO Options object and the GLO Meta object, the latter takes precedence.

ethereum options

An object representing the specific metainformation for Ethereum operations.

Within the meta.ledger.ethereum.native_transaction_content field, the following options are available:

Field	Type	Description
from	string (hexadecimal)	The Ethereum-native sender address that will be signing the transaction.
to	string (hexadecimal)	The receiving Ethereum-native address.
data	string	An optional field to include arbitrary data.
chainId	number or string (hexadecimal)	The id of the chain to prevent replay attacks. For more information, see EIP-155
nonce	string (hexadecimal) or number	A sequentially incrementing counter which indicates the transaction number from the account
value	string (hexadecimal) or number	The amount of ether to transfer in WEI (the smallest denomination of ether).
gasPrice	string (hexadecimal) or number	The price per unit of gas in WEI that the sender is willing to pay.
gasLimit	string (hexadecimal) or number	The maximum amount of gas that the sender is willing to spend on the transaction.

For more information, see Ethereum transactions.

Example:

{
  "ledger": {
    "ethereum": {
      "version": "0.0.1",
      "native_transaction_content": {
        "from": "0x1234567890123456789012345678901234567890",
        "to": "0x1234567890123456789012345678901234567890",
        "data": "0x1234567890123456789012345678901234567890",
        "chainId": 1,
        "nonce": 0,
        "value": 0,
        "gasPrice": 0,
        "gasLimit": 0
      }
    }
  }
}

Resource Locator object

A resource locator object contains the information to retrieve wallets, smart contract template, or instance details from MARCO or DLT network.

This object has the following fields:

Field	Type	Description
lookup_service.type	string	Required. Lookup service to use. Available values: marco, ledger.
lookup_service.value	string	Required. Specific lookup service. It varies depending on the type selected.
resource	string	Required. Resource identifier in the lookup service.

marco type

When lookup_service.type is set to marco, the lookup_service.value field must be set to marco.

The resource field is the MARCO platform's wallet, smart contract template, or instance identifier.

Example:

{
    "lookup_service": {
        "type": "marco",
        "value": "marco"
    },
    "resource": "WAL-62EPFgDCGOM"
}

ledger type

When lookup_service.type is ledger, the lookup_service.value field can be set to any of the following DLTs:

• ethereum: Ethereum network.
• hyperledger-fabric: Hyperledger Fabric network.

info

lookup_service.value must match the DLT where you want to execute the operation.

The field resource is the account or smart contract address in the DLT network.

Example:

{
    "lookup_service": {
        "type": "ledger",
        "value": "ethereum"
    },
    "resource": "0xfea8e07b145bb611a4b5ab5c015f3cc3644c083a"
}