Introduction to DAML

3 min readMay 31, 2022

DAML (Digital Asset Modelling Language) is an open-source smart contract language that allows the implementation of business logic without worrying about which DLT platform or database suits the use case. Official documentation can be found here https://docs.daml.com.

Install DAML SDK by referring steps in https://docs.daml.com/getting-started/installation.html

DAML Features

Privacy and Fine-grained Permission: While writing the smart contract, permissions like who can sign the contract creation, view, update and act on it can be specified. Daml transactions are composed of sub transactions and every sub transaction has its own set of witnesses that are entitled to see that part of the overall execution thus allowing sub transaction privacy.
Scenario-Based Testing: Daml Plugin for Visual Code IDE allows to write test case scenarios which allow visualizing the consequences of executing smart contract functionalities. Testcases also allow the creation of multiple test parties thereby allowing to test the smart contract as if it is deployed in a real Daml network.
Easy Development: The Daml plugin evaluates the smart contract in real-time, thereby allowing enabling developers to follow fast test-driven development practices. Daml Assistant is a command-line tool helps in installing new daml version, creating daml project using templates, build the project, launch SDK tools namely Sandbox, Navigator, HTTP JSON API service, codegen (to generate Java, Scala, and JavaScript/TypeScript classes representing daml contract templates) and many more.

DAML Smart Contract

Now, let us learn how to write a simple smart contract and run it on DAML Sandbox. Use VSCode for better experience. DAML Plugin is available for VSCode which allows for syntax highlighting, code autocomplete, testing, data visualization etc.

After successful installation of DAML SDK, use the command

daml new <app_name> --template <template_name>
Eg: daml new app1 --template empty-skeleton

This creates a DAML project with daml.yaml and daml folder. daml.yaml is the configuration file which specifies sdk-version, app name, version, dependencies and many more. In daml folder, keep all the daml smart contract files.

Here, Asset.daml file is created and added to daml folder.

Asset : This defines Asset properties and actions which can be taken on Asset

module Asset whereimport Daml.Script-- class like structure defining the fields & choices of a contract
template Asset
  with
    assetName : Text
    assetType : Text
    owner : Party
    issuer : Party
  where
    -- parties who must sign for a valid asset
    signatory owner, issuer
    -- actions available on a contract
    choice ProposeTransfer : ContractId AssetTransferProposal with
      newOwner : Party
    controller owner
      do
        create AssetTransferProposal with asset = this, newOwner

Notes:

template is the keyword to define a state similar to class in Java.
Specify the fields in the template which should necessarily contain a party who will be the signatory
Signatory refers to parties who must sign inorder to create or archive the contract
template can have choices which act on the contract to do certain actions. controller will perform this choice.

AssetTransferProposal : To transfer the asset to different party, we need the signature form the new owner which can get via initiate-accept pattern. Here observer party who will be the new owner to whom this asset should be transferred.

template AssetTransferProposal
  with
    asset : Asset
    newOwner : Party
  where
  signatory asset.owner
  -- parties who would be observing the contract and its evolution
  observer newOwner  choice Accept : ContractId Asset with
    controller newOwner
      do
        create asset with owner = newOwner  -- Reject transfer
  choice Reject : ContractId Asset with
    controller newOwner
      do
        create asset-- Withdraw transfer
  choice Withdraw : ContractId Asset with
    controller asset.owner
      do
        create asset

Testing

Daml allows us to write testcases to verify the smart contract functionalities and visualize the flow in VSCode itself. Here we can execute all the functionalities which we have defined for a template. We need to add daml-script dependency in daml.yaml and import Daml.Script in the module.

testAsset = script do  -- test parties
  issuer <- allocateParty "Samsung"
  party1 <- allocateParty "Raam"  -- create an asset
  assetTV <- submit issuer do
    createCmd Asset with
      assetName = "TV"
      assetType = "Electronics"
      owner = issuer
      issuer  -- proposal for transferring the asset
  proposal <- submit issuer do
    exerciseCmd assetTV ProposeTransfer with
    newOwner = party1  -- accept the transfer
  transferredAssetTV <- submit party1 do
    exerciseCmd proposal Accept
  
  return ()

To learn more about DAML Smart contract development, go through the official documentation https://docs.daml.com/daml/intro/0_Intro.html. Refer the cheetsheet for any quck reference https://docs.daml.com/cheat-sheet/.

Introduction to DAML

Written by Shivaganesh