Parser backends

sysml2kit does not implement the SysML v2 grammar. Reading textual notation goes through a ParserBackend (see sysml2kit.backends.protocol):

from sysml2kit.backends import get_backend

backend = get_backend("sysmlpy")
model = backend.parse(text)
model = backend.parse_files([path_a, path_b])

The sysmlpy backend

pip install sysml2kit[parse] installs sysmlpy (MIT, ANTLR4-based). The backend parses with sysmlpy.load_grammar_antlr and walks the raw ANTLR dict — sysmlpy's own wrapper loader rebuilds usage bodies lossily, so the wrappers are not used.

Fidelity: names, short names, docs, feature typing (including cross-package), multiplicity, attribute values with units, requirement subjects, and satisfy statements survive a text parse. What cannot round-trip is what sysmlpy's visitor discards before we see it: dependency statements (how the writer emits verify/derive), allocate and connect endpoints, and verification cases (filed upstream as sysmlpy #4 and #5). The fidelity table lives in SPEC.md and is pinned by tests/test_backend_fidelity.py. Use JSON interchange when you need the full traceability graph.

The dependency is capped (sysmlpy>=0.36.2,<0.37) because it has a single maintainer; bumps are deliberate, after reading the release notes.

Conformance oracle

A scheduled workflow (conformance.yml) downloads the EPL-2.0 OMG pilot implementation at run time (never vendored) and checks it accepts every .sysml file our writer emits. See tools/conformance/run_oracle.py.