The Frontmatter

Every template begins with a --- frontmatter header declaring its inputs. The whole block is consumed (nothing leaks into the output); the body then uses bare ${ name } references — no inline types.

---
params {
  service:  iri
  endpoint: iri optional
  classes:  iri[] min 1
  tags:     string[] optional max 5
  people:   { id: iri, name: string optional }[] min 1
  limit:    int
}
---

• Sections are brace-delimited. params { … } is mandatory; example … { … } blocks are optional (see Example blocks). params and example are keywords only here, so any parameter name is allowed.
• Types: iri, pname, string, int, decimal, double, bool, date, dateTime, time, literal(<dt>), term, raw.
• Modifiers (in order): <type> ['[]'] ['optional'] ['min' N] ['max' N]. [] marks an array; min/max bound its length; optional marks that a value may be omitted.
• raw inserts verbatim with no escaping — the single auditable unsafe hatch, visible in the header.

The engine validates the whole context against the header up front (missing required, unknown key, wrong type, out-of-range cardinality). Typing is strict: "10" is not an int, a list is not a scalar.

Values

${ name } / ${ p.id } reference declared params or loop variables. The same reference serializes differently by construct: standalone → per its declared type; inside $"…" → string-escaped; inside $<…> → percent-encoded.

Keywords and type names are case-insensitive; variable names, IRIs, and string content are case-sensitive.

Example Blocks

example dbpedia "DBpedia — people & orgs" {
  service: <http://dbpedia.org/sparql>
  classes: [ foaf:Person, foaf:Organization ]
  limit:   10
}

An example <id> ["<description>"] { … } block (in the --- frontmatter, alongside params) declares a named, validated set of sample values. They are development/preview fixtures, not production defaults: render(context) still requires real values, while previewExample(id) / a CLI renders with a set so a query is runnable while you develop. An IDE lists blocks by id and shows the description. Prefixed names resolve against the template’s PREFIX declarations.

Detection

A leading --- frontmatter header is a positive “this is a Triplate template” marker, complementing the fail-fast guarantee (the body is invalid host syntax until rendered).