Canton Daml Templates

Overview

A template is a type of contract that can be created — it defines the data a contract holds, who can see/act on it, and (with choices) what actions are possible. A contract is an instance of a template. Contracts are immutable: they are only ever created or archived.

Structure: template / with / where

template Token
  with
    owner : Party          -- create arguments (the contract's data)
  where
    signatory owner        -- whose authority creates/archives it

• template Token starts the definition (Daml is whitespace/layout-sensitive).
• The with block lists fields and types (: reads "of type"); these are in scope in the body.
• The where block holds the template body: signatories, observers, ensure, keys, and choices.

Signatories (required)

signatory names the parties whose authority is required to create or archive the contract — every template needs at least one. Daml guarantees signatories see all transactions that create or archive the contract.