dotjson dotgrammar FAQ
Usage Guide

Data Types

This section covers the core JSON data types supported by dotjson. Use it as a concept reference; keyword-level constraints live in the Constraints guide.

Type Overview

The type of a value in dotjson is specified using the type keyword. The basic types are:

  • string - Text data
  • number - Any numeric value (integer or decimal)
  • integer - Whole numbers only
  • boolean - True or false values
  • null - Null values
  • array and object - See the Structures guide for details

String

Strings represent text data.

Basic String 

{"type": "string"}

For string length, pattern, or format constraints, see the Constraints guide.

Number & Integer

Numeric types handle mathematical values with optional range constraints.

Difference Between Number and Integer

  • integer - Whole numbers only (e.g., -2, 0, 42)
  • number - Any numeric value including decimals (e.g., 3.14, -0.5, 42)

For numeric ranges like minimum/maximum, see Constraints.

Boolean

Boolean values represent binary choices - true or false. They’re ideal for flags, switches, and binary classifications.

Simple Boolean Field 

{
  "type": "object",
  "properties": {
    "isActive": {
      "type": "boolean",
      "description": "Whether the account is active"
    },
    "hasDiscount": {
      "type": "boolean",
      "description": "Whether a discount applies"
    },
    "requiresShipping": {
      "type": "boolean",
      "description": "Whether physical shipping is needed"
    }
  },
  "required": ["isActive"]
}
{
  "isActive": true,
  "hasDiscount": false,
  "requiresShipping": true
}

Boolean for Classification

Booleans are particularly useful for binary classification tasks:

{
  "type": "object",
  "properties": {
    "isSpam": {
      "type": "boolean",
      "description": "Whether the message is spam"
    },
    "isUrgent": {
      "type": "boolean",
      "description": "Whether immediate action is required"
    },
    "containsPii": {
      "type": "boolean",
      "description": "Whether personally identifiable information is present"
    }
  },
  "required": ["isSpam", "isUrgent", "containsPii"]
}
{
  "isSpam": false,
  "isUrgent": true,
  "containsPii": false
}

Null

The null type represents a null value. Use it in combination with other types (for example via anyOf) to make a field nullable. Optionality is separate: a field is optional if it is not listed in required.

Basic Null Type 

{
  "type": "object",
  "properties": {
    "placeholder": {
      "type": "null",
      "description": "Always null"
    }
  },
  "required": ["placeholder"]
}
{
  "placeholder": null
}

Nullable Fields

Combine null with other types using anyOf to allow a field to be present with a null value (nullable). The field remains required if listed in required.

{
  "type": "object",
  "properties": {
    "middleName": {
      "anyOf": [
        {"type": "string"},
        {"type": "null"}
      ],
      "description": "Optional middle name"
    },
    "alternateEmail": {
      "anyOf": [
        {"type": "string", "format": "email"},
        {"type": "null"}
      ],
      "default": null,
      "description": "Optional alternate email"
    }
  },
  "required": ["middleName", "alternateEmail"]
}

With values:

{
  "middleName": "James",
  "alternateEmail": "[email protected]"
}

Without values:

{
  "middleName": null,
  "alternateEmail": null
}

  Note

Optional fields: omit the field name from the required array to allow it to be omitted entirely.

Next Steps

Structures