Validate DocLang XML documents against XSD schema and Schematron rules.

pip install doclang

doclang validate my_document.dclg.xml

## Inject DocLang namespace if document doesn't declare it:
doclang validate my_document.dclg.xml --allow-empty-namespace

# XSD validation only
doclang validate my_document.dclg.xml --xsd-only

# Schematron validation only
doclang validate my_document.dclg.xml --schematron-only

# JSON output
doclang validate my_document.dclg.xml --format json

# Quiet mode (exit code only)
doclang validate my_document.dclg.xml --quiet

# Show help
doclang --help

from doclang import validate, ValidationError

try:
    validate("my_document.dclg.xml")
    print("Validation OK (no exception)")
except ValidationError as exc:
    print(exc)  # human-readable summary
    print(f"{exc.xsd_errors=}")
    print(f"{exc.schematron_errors=}")

Standard XML Schema Definition for structural validation:

• Document structure and element hierarchy
• Data types and attributes
• Element ordering

Additional business rules that XSD cannot express, using XSLT 3.0 and XPath 3.1:

<sch:pattern id="my-rule">
  <sch:rule context="dl:element">
    <sch:assert test="condition">Error message</sch:assert>
  </sch:rule>
</sch:pattern>

The validation uses XSLT 3.0 for modern XPath features.

In VS Code you can use Red Hat's XML extension and enable IDE-native XSD validation by adding the following to your settings.json (ℹ️ replacing the actual XSD path):

    "xml.fileAssociations": [
        {
            "pattern": "**/*.dclg.xml",
            "systemId": "file:///absolute/path/to/doclang.xsd",
        }
    ],

For this to work, the DocLang XML document must include the relevant namespace:

<doclang xmlns="https://www.doclang.ai/ns/v0">
    <!-- ... -->
</doclang>

Note that this approach does not cover Schematron validation rules.

• XSD 1.0 Specification
• ISO Schematron
• XPath 3.1 Specification