Write Off-Ledger Automation Using Daml

The Daml smart contract language is mostly meant to provide a way to define on-ledger logic, i.e. code that defines how a transaction happens on ledger. Daml is not meant to be used as a general purpose language that can interact with your file system or network; instead, the templates and choices defined with Daml are available to be used by off-ledger logic that interacts with the ledger API. Usually this off-ledger logic is written in a general-purpose language like Java or JavaScript and the codegen allows to interact with models defined in Daml without boilerplate.

However, there are times when it would be nice to write your off-ledger logic in Daml. For relatively simple automations that don’t require full access to your system’s capabilities, using Daml means that you don’t have to map from your on-ledger Daml types and their representation on a separate off-ledger general purpose language (either through the codegen or by manipulating the Protobuf representation of Daml types directly).

There are two tools that allow you to use Daml as an off-ledger language:

• Daml Script allows you to write automations that can be triggered by any off-ledger condition, such as the availability of a file in a folder, a message coming from a broker or a user interacting with the system directly.
• Daml Triggers allow a similar approach but triggered by on-ledger events, such as the creation of a contract.

In their interactions with a traditional database system Daml Scripts and Daml Triggers are analogous to SQL scripts and SQL triggers.