# pflow ontology

> A public vocabulary for Petri nets and the pflow ecosystem (go-pflow, pflow-rs,
> pflow.xyz, the book). Namespace https://ontology.pflow.xyz/ns#. Version 0.2.0, released 2026-10-26.
> Read-only. Queries run over the materialized graph (3835 triples), so
> subclass and dependency closure are already present.

Terms minted earlier in https://pflow.xyz/schema# are declared here as equivalent
to their old IRIs; "Arrow" there is "Arc" here.

## Query

- [SPARQL endpoint](https://ontology.pflow.xyz/sparql): SPARQL 1.1 protocol, read-only. SELECT, ASK,
  CONSTRUCT, DESCRIBE only. At most 1000 rows and 5 seconds per query; rate limited.
  Results are JSON (application/sparql-results+json) or CSV; graphs are N-Triples or Turtle.
- [MCP server](https://ontology.pflow.xyz/mcp): the same data as MCP tools (Streamable HTTP, no auth):
  sparql_query, describe_term, search_terms, list_classes, get_claim, get_release.
- [Term pages](https://ontology.pflow.xyz/term/liveness): one glossary concept per URL, as Turtle,
  N-Triples or HTML. Use describe_term or search_terms to find slugs.

## Download

- [Ontology, content negotiated](https://ontology.pflow.xyz/ns): Turtle, JSON-LD, N-Triples or RDF/XML
  by Accept header, or https://ontology.pflow.xyz/ns.ttl, /ns.jsonld, /ns.nt, /ns.rdf directly.
- [Whole release](https://ontology.pflow.xyz/release/pflow-ontology-0.2.0.tar): ontology in four formats, pack, certificate, manifest, verifier
- [SHA256SUMS](https://ontology.pflow.xyz/release/SHA256SUMS): per-file digests for sha256sum -c
- [verify-pack.py](https://ontology.pflow.xyz/release/verify-pack.py): recomputes the pack digests with only the Python standard library
- [Bibliography (BibTeX)](https://ontology.pflow.xyz/bibliography.bib): every reference in the ontology, for citing
- [Dataset description (VoID)](https://ontology.pflow.xyz/.well-known/void)

## License

The ontology is dedicated to the public domain under CC0 1.0 Universal
(https://creativecommons.org/publicdomain/zero/1.0/). Use it for anything, with no attribution required. This covers the
ontology data, not the source code of the projects it describes.

## Notes

- The downloadable ontology is the asserted one; the SPARQL graph also holds the
  RDFS/OWL-RL consequences. The certificate covers the RDFS rules only.
- Pack content digest: 82ef8da52b1ab0d41a26ea9c59131448e0aaae312fbf40fc161629d5755cd3da