Types

The schema type system defines what values are valid for a property. A type is specified via the type field on a Property item, as a URL that identifies the type.

When to reach for it

Set type on a property when the property's value must conform to a specific format — a valid integer, a parseable date, a URL with a scheme. When type is omitted, no type validation runs and any string value is accepted.

Primitive types

Primitive types are hosted at https://schema.host/ and provide built-in format validation at write time.

Syntax

<meta itemprop="type" content="https://schema.host/Integer">

Validation examples

Enum types

An enum is a named type whose valid values are listed explicitly. Declare it as a https://schema.host/Enum item in any schema document, then reference its URL from a property's type:

<div itemscope itemtype="https://schema.host/Enum">
  <meta itemprop="name" content="https://example.com/Status">
  <meta itemprop="value" content="active">
  <meta itemprop="value" content="retired">
</div>

<div itemprop="property" itemscope itemtype="https://pagelove.org/Property">
  <meta itemprop="name" content="status">
  <meta itemprop="type" content="https://example.com/Status">
</div>

The enum's identifying URL may be declared with itemprop="name" or itemprop="type" — both forms are accepted.

A write whose property value is not in the enum's value list is rejected with a 422 whose message names the offending value and the permitted list:

[https://example.com/Gadget].status: Value "sideways" is not a valid
https://example.com/Status (expected one of: "active", "retired")

Enums declared in your host's own schema documents override a platform enum with the same URL, the same way host-local schemas override system schemas.

Nested schema types

When type is a URL that matches another schema's governed type, the property value must be a nested [itemscope] element with that itemtype. The nested item is validated recursively against its own schema — cardinality, type, @validate, and group constraints all apply.

<div itemprop="property" itemscope itemtype="https://pagelove.org/Property">
  <meta itemprop="name" content="address">
  <meta itemprop="type" content="https://example.com/Address">
  <meta itemprop="cardinality" content="0..1">
</div>

A data item using this property:

<div itemscope itemtype="https://example.com/Person">
  <span itemprop="name">Alice</span>
  <div itemprop="address" itemscope itemtype="https://example.com/Address">
    <span itemprop="street">123 Main St</span>
    <span itemprop="city">Springfield</span>
  </div>
</div>

The nested Address item is validated against the https://example.com/Address schema. The self binding for a nested schema-level @validate is the nested [itemscope] element, not the parent.

Unknown types

A type URL that matches neither a primitive, a declared enum, nor a known schema is silently ignored — no type validation runs and any value is accepted. This allows forward-compatible use of type URLs before their schemas are defined.

How type validation runs

Type validation runs alongside cardinality checks, before property-level @validate expressions. The check operates on the text value extracted from each [itemprop] element — for elements with a content attribute (e.g. <meta>), the content value is checked; for other elements, the text content is checked.

Type violations are collected together with cardinality violations and reported in a single 422 response, so the reader can fix all shape errors in one pass.

Error cases

See also

• Property — where types are declared
• Schema — the parent schema item
• Schema definitions in HTML — how pagelove.mjs maps types to element shapes