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).
• visit::Visit and visit::VisitMut — a read-only and a mutating traversal, exhaustive over every AST node, for finding, replacing or removing conditions without writing a recursive walk.
• Source spans: every IdentifiedPath and every WHERE condition carries an ast::Span (a byte range of the source), so a diagnostic can name a position without echoing the text there. Spans take no part in equality.
• bind::bind — binds ITS-REST query_parameters into the AST as typed literals the printer escapes, at every position the grammar admits a parameter; an unbound, unknown, duplicate or unbindable parameter is reported by name, never by value.
• The federation feature: federation::parse_federated lifts the federation-only FROM ENDPOINT p [ … ] / ORGANISATION [ … ] directive out of a query and parses the rest as strict AQL, which to_aql renders without it; federation::to_federated_aql renders it back.
• 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 1.97 (edition 2024).

License

Business Source License 1.1 (LICENSE, SPDX BUSL-1.1), the licence of the FerroEHR application: all non-production use is free, production use is free for Non-Commercial Purposes, and any other production use, hosting for third parties or distribution for a fee needs a commercial licence from the Licensor, Vernum Projecten B.V. Each version becomes Apache License 2.0 four years after it is published. The crate is hand-written; the openEHR specification text it implements is the authority but is not embedded in the package. Versions up to 0.0.59 were published under Apache-2.0 and keep it.

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.