marc-bibframe

Convert MARC records to BIBFRAME RDF in Python, using the Library of Congress marc2bibframe2 XSLT.

The stylesheet is vendored in this package, so there is nothing to install alongside it and no Java or Saxon involved, just lxml, pymarc and rdflib.

Install

pip install marc-bibframe

Command line

You can use it from the command line:

$ marc-bibframe record.mrc
$ marc-bibframe record.xml --format json-ld --baseuri https://example.edu/catalog/
$ yaz-marcdump -o marcxml big.mrc | marc-bibframe -f nt -o big.nt

Binary MARC21 and MARCXML are both accepted and told apart by their content, so there is no flag for it. With no filename it reads standard input.

--format takes turtle (the default), json-ld, ntriples, xml, or rdfxml. The last is the stylesheet's own output passed through without a parse into rdflib, which is faster and keeps the transform's exact shape.

marc-bibframe --help lists the stylesheet parameters, which are also available as flags.

Use as a library

Or you can use it as a function in your own Python programs:

from marc_bibframe import marc_to_graph

with open("record.mrc", "rb") as fh:
    graph = marc_to_graph(fh, baseuri="https://example.edu/catalog/")

print(graph.serialize(format="turtle"))

MARCXML is accepted directly, and RDF/XML is available if you would rather not pay for a parse into an rdflib.Graph:

from marc_bibframe import marc_to_marcxml, marcxml_to_graph, marcxml_to_rdfxml

marcxml = marc_to_marcxml(open("record.mrc", "rb").read())
graph = marcxml_to_graph(marcxml)
rdfxml = marcxml_to_rdfxml(marcxml)

All four functions accept the stylesheet's parameters as keyword arguments — baseuri, idfield, idsource, localfields, bcp47_inference and generation_datestamp. See the docstring on marcxml_to_rdfxml for what each one does.

A note on the URIs it mints

MARC does not identify most of what it describes, so the transform invents URIs for them, built from baseuri and the record's own id:

https://example.edu/catalog/99123456#Work
https://example.edu/catalog/99123456#Instance
https://example.edu/catalog/99123456#Agent100-3
https://example.edu/catalog/99123456#Topic650-5

These are not authority URIs. They are scoped to the record they came from, so two records describing the same person produce two different agent URIs. If you need them reconciled against an authority (LC, Wikidata, your own store) that happens after this library hands you the graph.

For the same reason the default baseuri is http://example.org/, matching the stylesheet's own. Pick something under your control, and prefer a namespace that cannot be mistaken for an authority's: minting http://id.loc.gov/resources/99123456#Agent100-3 produces URIs that look like LC's but are not.

Keeping up with upstream

src/marc_bibframe/xsl/ is a copy of the LC stylesheets — see UPSTREAM for the tag and commit. Local changes are not edited in place; they live as patches in patches/ and are reapplied on every re-vendor:

./scripts/vendor.py v3.2.0

If a patch stops applying the script says so and stops, which is usually the signal that it was fixed upstream and can be deleted. The aim is to keep patches/ empty; anything in there should also be reported to LC.

The test suite checks the vendored tag against LC's latest release and fails when there is a newer one, with the command to run. It skips rather than fails if the GitHub API is unreachable.

The stylesheets are CC0. This wrapper is MIT.

Reproducible output

The transform stamps the current time into the work's admin metadata. generation_datestamp (--datestamp) overrides it, which makes the RDF/XML byte-for-byte reproducible. The other serializations still vary between runs: rdflib mints fresh blank node labels every time it serializes.

Development

uv sync
uv run pytest