[adding the Tracking-Neverending project to tasks blocking (now deprecated) T4007 as part of T93366]

I'm investigating making https://www.mediawiki.org/wiki/Extension:FileAnnotations implement the W3C standard for annotations ( https://www.w3.org/TR/annotation-model/ ) and REST API ( https://www.w3.org/TR/annotation-protocol/ ). These are based on the LinkedData standard, so it seems the functionality in this bug would be a prerequisite.

At the moment, I'm stuck on supplying a proper LD context for Wikidata properties. As I understand it, https://www.wikidata.org/wiki/Special:EntityData/Q142.ttl uses wdt:P18 and wdt is http://www.wikidata.org/prop/direct/ so in theory an application/ld+json request to http://www.wikidata.org/prop/direct/ ought to return a proper context which would let me use "@type": "P18" in the LD json of my annotation.

Does that make sense? I'm still very new to this linked data stuff.

See also T164655: Store and serve annotations in W3C standard format where I try to flesh out the JSON-LD for annotations.

Unfortunately neither Daniel nor me quite understand how those two things go together. I suggest we talk about it at the hackathon if that works for you.

As Lydia says, it's a bit unclear to us what FileAnnotations has to do with Wikidata RDF. But here's a few bits of information that could be relevant:

• Wikibase does not support JsonLD at all. We support Turtle, N-Triples and XML serialization for RDF, and we support our native JSON representation, which has nothing to do with RDF.
• http://www.wikidata.org/prop/direct/P18 currently redirects directly to http://www.wikidata.org/wiki/Property:P18. We should probably change that, so it redirects to http://www.wikidata.org/wiki/Special:EntityData/P18, which does content negotiation (but will give you a 406 if you ask it for application/ld+json).

It appears that we could support JSON-LD format without much trouble, which is the basis of the W3C Linked Data platform. In fact, there already exist JSON-LD processors for PHP, like https://github.com/digitalbazaar/php-json-ld and https://github.com/lanthaler/JsonLD -- the later of which is available in composer and already offers a conversion from N-Quads to JSON-LD.

It is possible our "native JSON respresentation" could be transformed into compliant JSON-LD by the simple addition of a @context property and an appropriate MIME type. I'd have to look into that.

This project relates to https://commons.wikimedia.org/wiki/Commons:Structured_data in so far as we eventually want to be able to annotate images with Wikidata relations. See https://www.mediawiki.org/wiki/Extension:FileAnnotations/Design#Research_and_User_testing and T146397: Edit interface should be nicer for mockups. These would be of the form "M18 is-image-of Q42" if I understand the current commons structured data proposal correctly.

@cscott making our JSON LD-compatible by just adding @context sounds tempting. But if I understand correctly, this would mean we now have two incompatible RDF representations of our data. That sounds like asking for trouble.

@daniel I don't think they are incompatible. They are both W3C standards; I believe JSON-LD is just an alternate representation of the RDF data. In fact, it ought to be "more compatible" than publishing an alternate JSON representation which is *not* grounded semantically. But I'm quickly leaving my depth here: if you think it would be helpful I can connect you to the editor of the JSON-LD spec (who I met at the I Annotate conference at the beginning of the month) who'd be better placed to answer.

@cscott you said "I believe JSON-LD is just an alternate representation of the RDF data" - that's exactly the problem. If we base the JSON-LD on our native JSON, the resulting RDF would not be compatible with our manually defined RDF mapping. It would have a different semantic grounding. We would end up with two incompatible RDF models.

To avoid this, our JSON-LD would have to be based on our RDF binding, not our native JSON. So it would look very different from our native JSON (and would probably be much more complex).

Change 371446 had a related patch set uploaded (by C. Scott Ananian; owner: C. Scott Ananian):
[purtle@master] Add JSON-LD support.

https://gerrit.wikimedia.org/r/371446

Change 379509 had a related patch set uploaded (by Thiemo Mättig (WMDE); owner: Thiemo Mättig (WMDE)):
[purtle@master] Minor code structure clean ups in JsonLdRdfWriter

https://gerrit.wikimedia.org/r/379509

Change 371446 merged by jenkins-bot:
[purtle@master] Add JSON-LD support.

https://gerrit.wikimedia.org/r/371446

Change 379509 merged by jenkins-bot:
[purtle@master] Minor code structure clean ups in JsonLdRdfWriter

https://gerrit.wikimedia.org/r/379509

Change 379669 had a related patch set uploaded (by C. Scott Ananian; owner: C. Scott Ananian):
[purtle@master] Tweak JSON-LD support to generate more idiomatic JSON-LD

https://gerrit.wikimedia.org/r/379669

The patch has been merged, but https://www.wikidata.org/wiki/Special:EntityData/Q142.jsonld doesn't work yet. I assume a new version of purtle needs to be released, then wikidata's composer.json patched to require it? (https://gerrit.wikimedia.org/r/379669 is still waiting for review as well.)

@cscott Yes, this needs a release, and a version bump in composer.json. Also, jsonld needs to be added to the default of the entityDataFormats setting in Wikibase.default.php (and possibly to production config). JSON-LD also need to be added to RdfWriterFactory. The code should be self-explanatory.

I can do the release, but you'll probably want to wait until the "tweak" patch is in. But I can't review it, I have no clue if it's doing the right thing. A +1 from someone who knows more about JSON-LD would help.

@daniel RdfWriterFactory comes from purtle, and has already been patched to add .jsonld. The patch to Wikibase should look something like https://gerrit.wikimedia.org/r/384050 but I can't test this locally.

Change 379669 merged by jenkins-bot:
[purtle@master] Tweak JSON-LD support to generate more idiomatic JSON-LD

https://gerrit.wikimedia.org/r/379669

I removed this ticket from our sprint boards for the moment. The only remaining patch https://gerrit.wikimedia.org/r/384050 is work in progress, but I do not find it obvious what exactly is needed to get it out of that state. I suggest to focus on the not yet closed sub-tickets instead, and possibly create more sub-tickets if needed.

I also see https://gerrit.wikimedia.org/r/390321 waiting for an agreement. I'm willing to continue working on this patch, but it should be linked to a sub-ticket so we can properly track it.

Change 384050 had a related patch set uploaded (by C. Scott Ananian; owner: C. Scott Ananian):
[mediawiki/extensions/Wikibase@master] Enable JSON-LD entity export

https://gerrit.wikimedia.org/r/384050

Pinging @Lydia_Pintscher and @Lea_Lacroix_WMDE about whether we want to merge JSON-LD support with https://gerrit.wikimedia.org/r/384050 or defer it to 1.33. More details in the gerrit link.

Change 384050 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Enable JSON-LD entity export

https://gerrit.wikimedia.org/r/384050

JsonLD is now enabled on beta, see announcement