Definitions

The header's definition section — metadata, variables, and references.

Besides the schema, an Internet Object document's header can hold definitions. A definition is a key–value pair on its own line, introduced by a tilde ~:

~ key: value

There are three kinds of definition, distinguished by the key's prefix:

Prefix	Kind	Purpose
(none)	Metadata	Document-level data (paging, status, …). Surfaces in the output header.
@	Value variable	A reusable value referenced as @name. See Variables.
$	Reference (ref)	A reusable schema or type referenced as $name. See Schema References.

The special key $schema names the document's default schema.

Metadata

Bare keys carry document metadata. They appear under a header in the loaded result, separate from the data:

~ pageSize: 10
~ success: T
~ $schema: { name: string }
---
~ John
~ Jane

Variables and references

@ defines a value variable; $ defines a reusable schema (a ref). Both are then used by name:

~ @active: T
~ $address: { street, city }
~ $schema: { name: string, addr: $address, isActive: bool }
---
~ John, { Main St, NYC }, @active
~ Jane, { Oak Ave, LA }, @active

A document may be header-only. If there is no data, the header still ends with the --- separator.

See Also

• Header — where definitions live in a document

• Variables — value variables (@)

• Schema References — schema and type refs ($)

• Internet Object Schema