Varve.Turtle 0.1.0-preview.20

Varve.Turtle

N-Triples, N-Quads, Turtle and TriG, read and written over UTF-8, allocating exactly zero bytes per quad.

• All 883 cases of the W3C rdf11 Turtle, TriG, N-Triples and N-Quads suites and the rdf12 N-Triples and N-Quads syntax suites pass, with no exemptions. Syntax and evaluation both: an evaluation test's dataset is compared up to a bijection of blank nodes.
• Five ways in: a span, a ReadOnlySequence, a Stream, a Stream asynchronously, and a PipeReader — plus TurtleReader and NQuadsReader for pulling one quad at a time. The answer does not depend on how the input arrived: every suite input is parsed whole and then again split at each byte offset, and required to give the same quads, or the same error kind and position; and every suite input is read both ways round, push and pull, and required to give the same answer again.
• The recovery unit fits the syntax. N-Triples resumes after the next newline; Turtle, which has no line structure, resumes after the next . at nesting depth zero and outside a string or IRI, and a failed statement produces no quads at all — including ones a blank node property list inside it had already emitted.
• Canonical N-Triples and N-Quads output, RDF 1.2's (ADR 0061), so two canonical documents are comparable byte for byte; RDF 1.2's c14n suites gate it. A Turtle round trip is isomorphic rather than byte-identical, because blank node labels are the parser's; writing what was written reproduces it exactly.
• RDF 1.2 throughout: base directions and triple terms in N-Triples and N-Quads, and in Turtle and TriG the reified triples, triple terms, annotations, reifiers and version directive of the Working Drafts (ADR 0121), where the rdf12 suites gate them. The writer declares VERSION "1.2" on its own the moment it writes a construct RDF 1.1 cannot read, never silently.

TurtleOptions options = new() { Syntax = RdfSyntax.Turtle };

ParseResult result = TurtleParser.Parse(
    utf8,
    static (in QuadView quad) => Console.WriteLine(quad.Subject.Lexical.Length),
    in options);

Writing needs a TurtleWriter, because a Turtle document has state a single statement does not — the prefixes in scope, and in TriG the graph block that is open. It declares no prefix it was not given: a prefix nobody declared is one the reader of the output has to guess the meaning of.

using TurtleWriter writer = new(output, new TurtleWriteOptions());
writer.DeclarePrefix("ex"u8, "http://example.org/"u8);
writer.Write(in quad);

The quad handed to the callback points into the parser's own buffer and is valid only for that call — which the type system enforces, because a ref struct cannot be captured or stored. Call Materialise() to keep one.

Layer 2 of Varve, a .NET-native event-sourced RDF store and SPARQL toolkit. MPL-2.0.