> For the complete documentation index, see [llms.txt](https://docs.internetobject.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.internetobject.org/schema-definition-language/data-types.md).

# Schema Data Types

A schema constrains each member to a **type**. The type system is small by design: a handful of **base types**, plus a closed set of **shortcuts** — names that stand for a base type with preset constraints baked in. Every type is configured through its **TypeDef**, the fixed set of options it accepts.

## Base types

| Type                       | Validates                                    | Reference                                                                |
| -------------------------- | -------------------------------------------- | ------------------------------------------------------------------------ |
| `string`                   | Text                                         | [String Types](/schema-definition-language/data-types/string.md)         |
| `number`                   | An IEEE-754 number                           | [Numeric Types](/schema-definition-language/data-types/number.md)        |
| `bigint`                   | An arbitrary-precision integer (`123n`)      | [BigInt](/schema-definition-language/data-types/bigint.md)               |
| `decimal`                  | A fixed-precision decimal (`123.45m`)        | [Decimal](/schema-definition-language/data-types/decimal.md)             |
| `bool`                     | `true` / `false`                             | [Bool](/schema-definition-language/data-types/bool.md)                   |
| `date`, `time`, `datetime` | Temporal values (`d'…'`, `t'…'`, `dt'…'`)    | [Date and Time](/schema-definition-language/data-types/date-and-time.md) |
| `binary`                   | Byte data, written as base64 (`b'…'`)        | [Binary](/schema-definition-language/data-types/binary.md)               |
| `object`                   | A structured shape (a SchemaDef)             | [Object (SchemaDef)](/schema-definition-language/data-types/object.md)   |
| `array`                    | An ordered list of values                    | [Array](/schema-definition-language/data-types/array.md)                 |
| `any`                      | Any value; the default when no type is given | [Any](/schema-definition-language/data-types/any.md)                     |

A member written without a type defaults to `any`, so `name, age` declares two `any` members.

> `date`, `time`, and `datetime` are **their own types**, not subtypes of `string`. Earlier drafts described them as string-derived; they are temporal types with their own literal values. See [Date and Time](/schema-definition-language/data-types/date-and-time.md).

## Shortcuts

A **shortcut** is a built-in name equal to a base type plus preset constraints. It is not a new type — it is a convenient, validated configuration of a base type. A conformant validator MUST recognize every shortcut name.

| Base     | Shortcuts                                                                     | Each shortcut is…                                    |
| -------- | ----------------------------------------------------------------------------- | ---------------------------------------------------- |
| `string` | `email`, `url`                                                                | `string` with a built-in pattern                     |
| `number` | `int`, `uint`, `int8`, `int16`, `int32`, `uint8` (`byte`), `uint16`, `uint32` | `number` restricted to whole values in a fixed range |

See [Numeric Types](/schema-definition-language/data-types/number.md) for the full numeric family and ranges, and [String Types](/schema-definition-language/data-types/string.md) for `email` and `url`.

> **Reserved.** `int64`, `uint64`, `float32`, and `float64` are reserved for future use and are not yet validated by the reference implementation.

## TypeDef and MemberDef

Each type defines a **TypeDef** — the exact set of options it accepts (for example, `string` accepts `pattern`, `minLen`, `maxLen`; `number` accepts `min`, `max`, `multipleOf`). Supplying a type together with chosen options produces a **MemberDef**, the definition of a single member:

```ruby
name:  { string, minLen: 1, maxLen: 100 },   # a string MemberDef
score: { int, min: 0, max: 100 }             # a number MemberDef
---
~ John, 85
```

The first value in a MemberDef is the type; the second is the default; the third is `choices`. Remaining options are written as `key: value` pairs. An option a type does not define is rejected. Each type page lists its TypeDef in full.

## See Also

* [Overview](/schema-definition-language/internet-object-schema.md) — how schemas are built
* [TypeDef](/schema-definition-language/advanced-schema-concepts/typedef.md) — the option-contract model
* [MemberDef](/schema-definition-language/advanced-schema-concepts/memberdef.md) — types, constraints, optional/nullable/default
* [Numeric Types](/schema-definition-language/data-types/number.md) · [String Types](/schema-definition-language/data-types/string.md) · [Date and Time](/schema-definition-language/data-types/date-and-time.md)


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