YAML-LD support

[Ostrzyciel]

After a discussion with the JSON-LD WG, they pointed out that the future YAML-LD (now part of the JSON-LD WG charter) could be a good fit for RDF Messages, as an RDF Message Log serialization.

The YAML-LD draft spec already proposes to use the existing YAML feature called "YAML Streams" where subsequent YAML documents in one file are separated with ---. See the spec draft: https://json-ld.github.io/yaml-ld/spec/#streams

Example from that draft:

"@base": https://schema.org
"@id": https://w3.org/yaml-ld/
"@type": WebContent
name: YAML-LD
---
"@base": https://schema.org
"@id": https://www.w3.org/TR/json-ld11/
"@type": WebContent
name: JSON-LD

However, this is not really intended to denote discrete messages. A YAML-LD stream is transformed into an array at the root node in JSON-LD, yielding this:

[
  {
    "@base": "https://schema.org",
    "@id": "https://w3.org/yaml-ld/",
    "@type": "WebContent",
    "name": "YAML-LD"
  },
  {
    "@base": "https://schema.org",
    "@id": "https://www.w3.org/TR/json-ld11/",
    "@type": "WebContent",
    "name": "JSON-LD"
  }
]

See JSON-LD 1.1 section 4.1: https://www.w3.org/TR/json-ld11/#advanced-context-usage

These are NOT multiple JSON-LD documents; rather this is a single JSON-LD document with multiple contexts.

I see two ways out of this:

• A) we introduce new syntax (comments?) for RDF Message Logs and keep the YAML-LD usage of YAML Streams as-is
• B) we nicely ask the JSON-LD WG if they would be willing to drop the current use of YAML Streams in favor of reserving it for future use with RDF Message Logs.

I would try with B), because YAML-LD is not yet standardized and it can still be changed. It would also allow the JSON-LD group to later get for free compatibility between YAML-LD streams and NDJSON-LD.

Any opinions welcome!

[Ostrzyciel]

I just found this thread: w3c/yaml-ld#63

It seems that for example yq takes an approach where it aligns YAML Streams with NDJSON, not with the behavior used by the YAML-LD spec draft: w3c/yaml-ld#63 (comment)

The discussion did steer at some point to something very similar to RDF Messages: w3c/yaml-ld#63 (comment)

And, more importantly, see this log of discussion from TPAC 2022: w3c/yaml-ld#63 (comment)

The summary is:

Generally feeling that this may be useful beyond JSON-LD and YAML-LD, and something like an "LD Streams" framework might be useful which this could fit into.

I don't think there were strong voices against the interpretation I proposed in option B). If anything, the discussion leaned in that direction... but of course I am biased 😄

[jpcik]

Is there a way to have a discussion with them? Perhaps it's a matter of finding the right interlocutor

[Ostrzyciel]

In #14 I added the first draft of this format to the spec.

We should review this internally, and then try and schedule a meeting with JSON-LD people, I think.