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In this module, you’ll create a Concerto model that defines the data structure for your template. The model acts as a schema that specifies what data your template expects and how it should be structured.
Learn more about the Concerto modeling language and its runtime at concerto.accordproject.org

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What you’ll build

You’ll create a simple HelloWorld concept with a name property. This model will serve as the foundation for your template in the following modules.

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Creating your first model

Follow these steps in the Concerto Model editor to build your data model:
1

Define the model namespace

Open the Concerto Model editor and define the model namespace. The namespace provides a unique identifier for your model.
namespace [email protected]
The namespace follows the format name@version, which helps organize and version your models.
2

Create a concept

Define a new concept called HelloWorld. Concepts are the building blocks of Concerto models and represent data structures.
namespace [email protected]

concept HelloWorld {
}
3

Add the template decorator

Add the @template decorator to the concept. This decorator marks the concept as a template data model.
namespace [email protected]

@template
concept HelloWorld {
}
Decorators provide metadata about your model elements and enable special behaviors.
4

Add a string property

Add a string property called name to store the name value.
namespace [email protected]

@template
concept HelloWorld {
    o String name
}
The o prefix indicates this is an optional property. You can also use --> for relationships or add modifiers like [] for arrays.

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Complete example

Here’s the complete model you’ve created: 
namespace [email protected]

@template
concept HelloWorld {
    o String name
}

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Understanding the model

Your model now defines:
  • Namespace: [email protected] - uniquely identifies this model
  • Concept: HelloWorld - the data structure for your template
  • Decorator: @template - marks this as a template model
  • Property: name of type String - the data field that will be used in your template

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Real-world example

Here’s a more complex example from a product announcement template: 
namespace [email protected]

@template
concept ProductAnnouncement {
    o String productName
    o String description
    o DateTime releaseDate
}
This model includes multiple properties with different types, demonstrating how you can create more sophisticated data structures.

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Next steps

Now that you’ve defined your data model, proceed to Module 2: TemplateMark templates to create a template that uses this model.

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Key concepts

A namespace provides a unique identifier for your model and helps prevent naming conflicts. It follows semantic versioning (e.g., [email protected]) so you can evolve your models over time.
Concepts are classes that define data structures in Concerto. They can contain properties, relationships to other concepts, and decorators that add metadata.
Decorators are annotations that provide metadata about model elements. The @template decorator indicates that this concept represents template data, enabling special handling by the template engine.
Concerto supports various property types including String, Integer, Double, Boolean, DateTime, and custom concepts. You can also create arrays and optional fields.

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