- Add _ttl_block() helper to accumulate all predicate-object pairs before
writing, producing a single valid Turtle subject block terminated by one
period — eliminates the bug where rdfs:subClassOf / domain / range were
appended after a closed '.' block
- Add missing data_properties loop to _export_owl_turtle so
owl:DatatypeProperty declarations are no longer silently dropped
- Add _escape_ttl_str() to escape quotes, backslashes, newlines, carriage
returns, and tabs inside Turtle string literals (rdfs:label, rdfs:comment,
owl:versionInfo)
- Unify optional-field null checks to consistent x = prop.get(); if x: pattern
- Add 43 tests in tests/export/test_owl_exporter.py covering syntax validity,
data properties, string escaping, null handling, and header output
- Update CHANGELOG.md with [Unreleased] entry
Closes#478
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
