openehr-query

A hand-written openEHR AQL 1.1 front end for Rust: lexer, parser, and typed AST for the Archetype Query Language — native logos + chumsky, no ANTLR runtime.

What it provides

• A complete AQL 1.1 lexer and parser producing a typed AST (SELECT, FROM/CONTAINS, WHERE, ORDER BY, LIMIT, path expressions with predicates, parameters, functions), corpus-validated against the official grammar's example set.
• Typed parse errors: ParseError separates a lexing refusal (carrying the lexer's error as a real source()) from a grammar refusal (carrying every position the parser reported), so a caller branches on the failure instead of reading its message. Each grammar fault gives the position twice — as token-stream indices and as a byte range of the source, so a diagnostic can underline the offending text. Display is the located diagnostic to show a human; it names the token indices.
• lexer::lex_spanned — the token stream with each token's source byte span, additive beside lexer::lex. parser::parse_spanned consumes it and is what parser::parse_str runs; parser::parse over a bare &[Token] still works and reports token indices only.
• printer::to_aql — canonical AQL rendering of the AST, the parser's inverse, for programmatic query construction (corpus-verified fixed point: parse(to_aql(ast)) == ast).
• The AST is engine-agnostic: this crate deliberately stops at the syntax layer, so any execution engine (SQL generation, in-memory evaluation) can build on it.

Versioning

The package version is the crate's own independent SemVer line — it tracks this implementation's code and moves freely with fixes and improvements, never with the vendored openEHR specification. The implemented spec version is always available at runtime as the crate-level constant openehr_query::SPEC_VERSION ("1.1.0" — QUERY/AQL), independent of the package version.

Minimum supported Rust version

Rust 1.96 (edition 2024).

License

Apache License 2.0 (LICENSE-APACHE-2.0). The crate is hand-written; the openEHR specification text it implements is the authority but is not embedded in the package. The openehr-* crates are Apache-2.0 so any Rust project can use them; the Business Source License of the FerroEHR application does not apply to them.

Part of FerroEHR

This crate is the query-language layer of FerroEHR, a pure-Rust, openEHR-spec-conformant Clinical Data Repository (ITS-REST 1.1.0 + AQL 1.1 on PostgreSQL 18). The crates are usable standalone; FerroEHR is the reference consumer.