xsd-schema

xsd-schema is a Rust XML Schema validator for XSD 1.0 and 1.1 with a full post-schema-validation infoset (PSVI). Its push-based API integrates with event-based parsers such as quick-xml and DOM-style sources such as roxmltree, and a built-in XPath 2.0 engine adapts to any DOM through the DomNavigator trait.

Documentation

Document	Description
Introduction	Public API overview, feature sets, schema loading, validation flow, XPath entry points, and async loading notes.
Architecture Overview	Crate structure, pipeline diagram, module map, key abstractions, milestone history, and build reference.
Extensibility Guide	Extension points for annotations/appinfo, schema loaders, DOM navigation, and custom XPath functions.
Unsafe Code	Inventory of unsafe blocks, safety invariants, and Miri verification commands.
Composing XML from Rust	XPath 2.0 with Rust values bound as $variables, the Lisp-style form! constructor, iterator pipelines for the FLWOR clauses, and serialization.
Changelog	Release notes for every version, with upgrade notes for breaking releases.

To see exactly what the validator compiled for a complex type — the authored particle tree, the automaton it became, counters, and where each state comes from in the schema — use the content-model inspector: Inspecting a compiled content model.

To build XML from query results in Rust — XPath 2.0 with Rust values bound as $variables, iterator pipelines for the FLWOR clauses, and a Lisp-style constructor — use the composition layer: Composing XML from Rust.

Test Results

Suite	Command	Total	Passed	Failed	Skipped	Errors	Pass rate
W3C XSD 1.0	cargo test --test conformance --features xsd11 --release -- --test-suite ../../xsdtests --version 1.0	39,510	39,458	18	34	0	99.95%
W3C XSD 1.1	cargo test --test conformance --features xsd11 --release -- --test-suite ../../xsdtests --version 1.1	2,319	2,313	6	0	0	99.7%
XQTS XPath 2.0	cargo test --test xqts_xpath --features xsd11 -- -s ../../XQTS_1_0_2 --all -v -f	8,047	8,047	0	0	0	100.0%

All 18 remaining XSD 1.0 failures and all 6 XSD 1.1 failures are documented disputes: W3C-queried tests (Bugzilla 4146/4680/4957/6901/29085), tests that contradict other accepted tests in the same suite (the elemM002 / xsd015.e family vs. Saxon's Missing group), or documented waivers.

Benchmark

Instance-validation throughput and memory for xsd-schema's three ingestion strategies, over a synthetic dataset ≈ 15.56 MB — validated against its XSD. Each strategy runs in its own subprocess (so RSS deltas are clean), timing is averaged over 10 iterations, and the schema is compiled once, off the clock.

• streaming — push-based, no DOM (drive_quick_xml + SchemaValidator)
• DOM (roxmltree) — third-party tree via the DomNavigator trait
• DOM (BufferDoc) — built-in compact 16-byte-node document

Strategy	Parser	Time	Throughput	RSS delta
streaming	quick-xml	308 ms	50.6 MB/s	568 KB
DOM (roxmltree)	roxmltree	265 ms	58.8 MB/s	88.4 MB
DOM (BufferDoc)	quick-xml	339 ms	45.9 MB/s	61.4 MB

Re-measured 2026-09-11 after the exact-occurrence, allocation-gate and precomputed-closure work (four runs per strategy, spread under 3 %); the previous table read 353 / 303 / 377 ms. Both W3C suites are unchanged by that work (failure lists byte-identical to v0.1.5).

AI Disclosure

This project was generated with AI as an experiment. The generated code and content were reviewed and refined by the author. Use of this repository is governed by its license, including any production use. This notice is provided for transparency.

Source Provenance

No third-party source repositories were used as rewrite sources for this codebase, with the sole exception of the author's own prior work:

• semyonc/xpath2 — C# XPath 2.0 implementation
• WmHelp XmlPad — earlier Delphi tool by the same author together with Edward Aponasko and Alex Pospelov

A small number of Microsoft .NET API shapes are mirrored where they map naturally onto the data model, but no Microsoft source code was ported or rewritten.