Your first document

We will describe a stationery catalog containing two products. The purpose is to make the information explicit and inspect the model that Nexus Script builds.

Prepare a folder

Use a current Nexus installation with NexusScript available on PATH. NexusScript /help prints the command-line options. The CLI is available on Windows and Linux; the commands below use the same arguments on both.

Create an empty folder for this chapter. Save this as Catalog.nxscript:

Catalog.nxscript

Catalog Shop {
    Title: "Corner Stationery";
    Currency: USD;

    Product Notebook {
        Title: "Pocket notebook";
        PriceCents: 450;
    }
    Product Pencil {
        Title: "Graphite pencil";
        PriceCents: 90;
    }
}

Read the first declaration as “a Catalog named Shop.” Its braces contain the information belonging to Shop. Title and Currency are properties. Each property has a colon, a value, and a terminating semicolon.

Product Notebook and Product Pencil are child definitions. They have their own properties and their own identities within Shop. Their closing braces do not take semicolons. This distinction lets a reader see where a value ends and where a nested definition ends.

Notebook is the definition's name, used to address it. "Pocket notebook" is the value of its Title property, used by our catalog application for display. Changing the title does not rename the definition.

Catalog, Product, Title, and PriceCents are vocabulary we chose for this model. No dialect or built-in product type is required to write this document.

Compile and inspect

From that folder, run:

NexusScript /input=Catalog.nxscript /output=Catalog.json

Open Catalog.json. Its domain content is:

{
  "Shop": {
    "Title": "Corner Stationery",
    "Currency": "USD",
    "Notebook": { "Title": "Pocket notebook", "PriceCents": "450" },
    "Pencil": { "Title": "Graphite pencil", "PriceCents": "90" }
  }
}

This display omits the actual output's _nx metadata so the structure is easy to see. Metadata records such things as kinds and source locations; it does not replace your domain properties. Artifacts explains the full output.

Notice that JSON uses Shop, Notebook, and Pencil as keys. The language does not invent a Products wrapper from the kind Product. Also notice that 450 is emitted as text. Nexus Script's scalar data is text; a dialect or consumer can require that text to represent an integer. No price calculation or currency conversion happened during compilation.

Change the model

Change Notebook's PriceCents to 500 and compile again. Only the corresponding effective value changes. Add a third Product with another name and it becomes another child of Shop.

Now imagine that the catalog has a featured product, several products share defaults, and different regions need different prices. References, composition, and targets will express those relationships in the following chapters.

Continue with Structure, values, and identity.