The `trn:` namespace

http://purl.org/stuff/transmissions/, prefix trn:.

Every published plugin profile in this project, in plugin-universe, in downspout and in JigDAW writes IRIs in this namespace. Until 2026-09-18 every one of them resolved to a 404. They resolve now.

What resolves where

Request	Answer
`http://purl.org/stuff/transmissions/`	302 to `https://purl.org/stuff/transmissions/`, then to `https://hyperdata.it/xmlns/transmissions/`
`https://hyperdata.it/xmlns/transmissions/`	the page, or `transmissions.ttl` when `Accept` asks for RDF
`https://hyperdata.it/xmlns/transmissions`	301 to the form with the trailing slash
`https://hyperdata.it/xmlns/transmissions/transmissions.ttl`	the vocabulary, `text/turtle`
`https://hyperdata.it/xmlns/transmissions/PluginProfile`	303 to the namespace IRI

The PURL redirect already existed: purl.org/stuff/<name> maps to hyperdata.it/xmlns/<name> through a wildcard, and JigDAW uses the same one. Nothing at purl.org needed changing. The only thing missing was anything at the far end.

Two decisions are load bearing and are stated in deploy/nginx/vocab.conf beside the lines that implement them.

A term answers 303, not 200. trn:PluginProfile denotes a class. Answering 200 would assert that the class is the page returned, and a reasoner that conflates the two starts inferring that a class is a document.

Everything carries Access-Control-Allow-Origin. JigDAW’s host runs in a browser and dereferences these IRIs. A response without the header is unreadable rather than merely untrusted.

Minting

The namespace ends in a slash and terms are trn:Foo, not trn:vocab#Foo. It is minted on the PURL and never on hyperdata.it: the PURL is the identity and the host is an implementation detail. Minting on the serving domain would break every IRI ever published the day the site moves, including the ones written into other people’s files.

Building and deploying

vocabs/ holds the terms, split by subject. The served document is all of those files concatenated, because the namespace is one thing and the sources are several.

npm run build:vocab     # regenerates deploy/vocab/
npm run check:nginx     # validates deploy/nginx/vocab.conf in a container
npm test                # tests/vocab/site.test.js fails if deploy/vocab is stale

deploy/vocab/ is generated and committed, because nginx serves it out of the checkout on the server and there is no build step there. tests/vocab/site.test.js fails if it has drifted from vocabs/, which is the only thing connecting the two.

On the server, once:

# inside the existing `server { server_name hyperdata.it; ... }` block,
# beside the JigDAW one
include /home/github/transmission/deploy/nginx/vocab.conf;

cd /home/github/transmission && git pull
sudo nginx -t && sudo systemctl reload nginx

To check it:

curl -sS -H "Accept: text/turtle" https://hyperdata.it/xmlns/transmissions/ | grep -c '^trn:'
curl -sS -o /dev/null -w '%{http_code}\n' https://hyperdata.it/xmlns/transmissions/PluginProfile

Expect the term count and 303. Piping the document into head makes curl exit 23, which is head closing the pipe on a 42 kB body rather than anything being wrong; grep -c and sed -n read to the end and exit 0.

Adding a term afterwards is npm run build:vocab, commit, and git pull on the server. No nginx reload: the files are read from disk on every request.

What is in the document, and what is not

vocabs/ holds seven files and the served document is all of them:

File	What
`ontology.ttl`	the namespace’s own description
`profile.ttl`	what a plugin is musically: roles, signal types, routing
`project.ttl`	the saved project: graph, nodes, connections, transport, arrangement
`parameters.ttl`	the parameter terms downspout’s profiles use
`formats.ttl`	plugin formats, and the terms retired in favour of `lv2:`
`actions.ttl`	the actions an agent can ask a host to perform
`djset.ttl`	DJ set lists

208 terms. Every trn: IRI named in src/rdf/Vocabulary.js is declared in one of them, and tests/vocab/site.test.js fails if that stops being true. It was not true before: 50 of the 81 terms the code writes into every saved project were declared nowhere at all, and nothing reported it because nothing connected the two files.

formats.ttl came from plugin-universe’s vocabs/trn-extensions.ttl, whose own header asks for exactly that: “proposed upstream to ~/github/transmission rather than maintained separately”. Its copy stays where its SHACL shapes can see it, and the test compares the two when that checkout is present.

Instance data in the namespace

Saved projects bind the default prefix to this namespace:

@prefix : <http://purl.org/stuff/transmissions/> .

:main a :Transmission ; :pipe ( :bassgen :pulse :system-output ) .

So every patch node name is minted in the vocabulary namespace. Measured across the four repositories, 160 such IRIs exist in committed files: trn:pulse, trn:plugin-1, trn:harmonic-atlas, trn:plugins/downspout/ambo and the rest. They are data, not terms, and the vocabulary document does not define them.

deploy/nginx/vocab.conf 303s them to the namespace anyway, which is better than the 404 they would otherwise get, and is the ordinary behaviour of a slash namespace for an IRI it does not define. Fixing it properly means giving projects a namespace of their own and rewriting every committed project file, which is a larger and separate decision: the IRIs are already published, and changing them changes what every saved project says.

The trn: namespace