Schematron Rule Runner

Run an ISO/IEC 19757-3 Schematron schema against an XML document fully in the browser. Documented XPath 1.0 subset.

How it works

Schematron is the ISO/IEC 19757-3 standard for rule-based validation of XML structures. The runner follows the classic two-pass flow:

1. Parse the schema — the <schema xmlns="http://purl.oclc.org/dsdl/schematron"> file is read: every <pattern> holds <rule context="…"> entries which in turn hold <assert test="…"> or <report test="…"> nodes.
2. Evaluation — for each rule, the XPath in context is evaluated against the input document; on every matched node, the test XPath is evaluated. An assert that evaluates to false(), or a report that evaluates to true(), yields a diagnostic carrying the offending node's path and the rule's message.

Supported XPath subset

To stay 100 % client-side and fit in a tiny JavaScript bundle, we hand-roll a documented subset of XPath 1.0. Expressions outside this scope emit a E_XPATH_UNSUPPORTED diagnostic — never a silent mis-evaluation.

Supported

• Absolute paths (/Invoice/cbc:ID), relative paths from the context, ., .., *.
• Explicit axes child::, attribute::, self::, parent::.
• Attributes through @code.
• Numeric predicates ([1]), position(), last(), count(path) op N, comparisons =, !=, <, <=, >, >=.
• Boolean operators and, or, function not().
• Functions: count, string-length, normalize-space, string, number, boolean, true(), false(), position(), last().
• Arithmetic +, -, *, div, mod.

Not supported

• The descendant operator // and the descendant:: axis.
• The following-sibling::, preceding:: and similar axes.
• Functions local-name(), substring(), matches(), key().
• XPath 2.0+ (sequences, if/then/else, for $x in).

Examples

Click “Load example” to pre-fill both panes with a simplified version of EN 16931's BR-S-09 rule: every TaxSubtotal's VAT amount must equal the taxable amount times the rate divided by 100. The example is intentionally minimal — it illustrates the mechanism without requiring a full UBL document.

Limitations

• The runner does not resolve external <include> or <extends> directives: your schema must be self-contained.
• <ns> declarations are read but element prefixes are matched literally (cbc:ID in a test looks for an element tagged exactly cbc:ID).
• <value-of select="…"/> calls inside messages are rendered as {select} placeholders, without runtime interpolation.
• <phase> declarations are ignored: every rule is evaluated.

Privacy

Related documentation

• ISO/IEC 19757-3 — Schematron, the official standard. The historical site schematron.com remains an excellent pedagogical reference.
• PEPPOL Validator — ships the official EN 16931 + PEPPOL BIS 3.0 Schematron rules compiled into TypeScript.
• EN 16931 Validator — the underlying core-norm layer.