Keywords

The language reserves every $-prefixed key as a keyword. Everything else is bare and defined by the dialect: an element's type, its props, and the prop names inside props. Keywords fall into five groups.

Document

Identify a schema and its dialect:

Keyword	Purpose	Reference
`$id`	Identity and revision of a document	Documents
`$schema`	Dialect identifier of a document	Documents

Expressions

Resolve a prop value:

Keyword	Purpose	Reference
`$data`	Reference to a data field value	Data References
`$t`	Reference to a translatable message	Translation References
`$params`	Values interpolated into a message	Translation References
`$tags`	Elements rendering a message's tags	Translation References
`$arg`	Reference to a scoped argument	Scoped Arguments

Binding

Bind a prop to a data field:

Keyword	Purpose	Reference
`$field`	Two-way binding to a data field	Form Fields

$field appears in the same value positions as expressions, but it does more than read: it resolves a value and registers a two-way binding with form state. Every other value-position keyword is a pure read.

Actions

Dispatch handlers on callbacks:

Keyword	Purpose	Reference
`$action`	Name of the handler to dispatch	Actions
`$args`	Arguments passed to the handler	Actions

Control flow

Select or repeat a value:

Keyword	Purpose	Reference
`$if`	Binary conditional (schema validation)	If/Then/Else
`$then`	Value to use if the condition matches	If/Then/Else
`$else`	Value to use if it does not match	If/Then/Else
`$switch`	Multi-case conditional	Switch/Case/Default
`$case`	Case mapping for a switch	Switch/Case/Default
`$default`	Default branch for a switch	Switch/Case/Default
`$map`	Source array to map over	Maps
`$each`	Template applied to each mapped item	Maps

Some keywords are dependent and only valid alongside the keyword that governs them: $then and $else accompany $if; $case and $default accompany $switch; $each accompanies $map; $params and $tags accompany $t; $args accompanies $action.

Scoped argument names

Scoped arguments are reserved names, not keywords: they never appear as keys, only as string values read through the $arg keyword. An enclosing construct injects them into the scope beneath it:

Name	Injected by	Reference
`$item`	Maps	Scoped Arguments
`$index`	Maps	Scoped Arguments
`$content`	Translation tags	Translation References
`$0`, `$1`	Actions	Scoped Arguments

Structure

Bare, no $: type identifies an element; props carries its configuration. Every other bare key inside props is a dialect-defined prop.