RMT Reference: State, Selectors and Data

This page describes data sources, state and declarative derivations.

Syntax

Operator	Form	Allowed contexts	Parameters	Function	Diagnostics	Related operators
type	state app.count type number	state, input	type name	Declares the expected value type.	Missing types produce syntax diagnostics.	state, input
initial	initial true or initial { text "Ready" }	state	literal or initial block	Sets the initial value.	State blocks allow only initial values.	preserve
preserve	state app.status type object preserve	state, surface	flag without value	Preserves state or surface state across lifecycle boundaries.	Wrong contexts produce context diagnostics.	destroy releases
from	from state app.status	selector, datasource, operations, payload	source kind and reference	Binds a declarative source.	Source kind must be allowed.	endpoint, selector, payload
endpoint	from endpoint "/api/items"	datasource, operations	string or identifier	Binds host endpoint data.	Invalid source kinds are reported.	method, contract
sse	stream feed from sse app.feed	stream	stream identifier	Binds Server-Sent Events to streaming.	stream requires a source.	stream
worker	prewarm index from worker search.prepare	operations, datasource	worker identifier	Describes worker-based preparation.	Source kind must be static.	prewarm
fixture	fallback fixture app.sample	datasource, operations	fixture identifier	Binds test or fallback data.	Unknown references are reported semantically.	fallback
resource	from resource app.file	operations, resource	resource identifier	Uses an owner-scoped resource as source.	Missing resources produce semantic diagnostics.	resource, dispose
where	where item.active == true	selector	declarative expression	Filters selector results.	Function calls are not allowed.	find, sort by
find	find item.id == input.id	selector	declarative expression	Selects one record.	Invalid expressions are parser diagnostics.	where
sort by	sort by item.createdAt desc	selector	path, direction	Sorts selector results stably.	Sort clause must be complete.	output
output	output MessageList	selector	type name	Names the output contract.	Missing type produces syntax diagnostics.	selector
method	method GET	datasource	HTTP method or identifier	Documents the host method.	Only valid in datasource blocks.	endpoint
contract	contract "xtend.schema.v1"	datasource	static string	Binds a data or endpoint schema.	Wrong context is reported.	result
result	result list	datasource	result shape	Describes the expected result shape.	Datasource clause only.	fallback
fallback	fallback fixture app.empty	datasource, remote surface	kind and reference	Declares a safe replacement path.	Missing reference is reported.	fixture, fallback surface

Allowed contexts

State clauses belong in state, selector clauses in selector, datasource clauses in datasource. Source kinds appear after from or fallback.

Parameters

Identifiers reference records; strings describe external paths or contracts; directions such as asc and desc remain static.

Description

RMT separates stored state, derived view models and host data sources. This lets the compiler understand dependencies without evaluating host JavaScript.

Examples

template reference.data {
  state app.filter type object preserve {
    initial {
      text "open"
    }
  }

  datasource tickets from endpoint "/api/tickets" {
    method GET
    contract "xtend.ticket-list.v1"
    result list
    fallback fixture tickets.empty
  }

  selector openTickets from datasource tickets {
    where ticket.status == "open"
    find ticket.id == app.filter.text
    sort by ticket.createdAt desc
    output TicketList
  }

  portal app.root root "#app" layer surface
  surface list kind region component x-summary {
    portal app.root
    lane visible weight 70 {
      hydrate ticket.list from selector openTickets
    }
  }
}

Diagnostics

The parser reports wrong clauses in each block. The semantic graph reports unknown state, selector, datasource, fixture or resource references.

Related operators

state, selector, datasource, action, hydrate, stream, when.

Related reading

The RMT reference index links state, selector, and data records to their lifecycle rules. Related article