Alias a JSON-LD keyword and simultaneously provide a @context for it

Question

I have the following JSON document (based on GitHub API output):

{
  "@id": "https://github.com/octadocs/octadocs",
  "license": {
    "key": "mit",
    "name": "MIT License",
    "spdx_id": "MIT",
    "url": "https://api.github.com/licenses/mit",
    "node_id": "MDc6TGljZW5zZTEz"
  }
}

Using JSON-LD, I'd like to retrieve the following triple from this:

<https://github.com/octadocs/octadocs>
    <https://octadocs.io/github/license>
    <https://spdx.org/licenses/MIT> .

I can interpret license as https://octadocs.io/github/license with @vocab (I would like to use it globally actually, for all properties);
I can specify @type for spdx_id to make its value an IRI;
and I finally can define a @context with a @base for it, to convert MIT string into an spdx.org reference.

Context:

{
  "@base": "https://octadocs.io/github/",
  "@vocab": "https://octadocs.io/github/",
  "spdx_id": {
    "@type": "@id",
    "@context": {
      "@base": "https://spdx.org/licenses/"
    }
  }
}

See a demonstration in JSON-LD playground.

But, this creates a slightly different structure than the desired one:

<https://github.com/octadocs/octadocs> <https://octadocs.io/github/license> _:b0 .
_:b0 <https://octadocs.io/github/spdx_id> <https://spdx.org/licenses/MIT> .

I'd like to avoid the blank node.

This can be achieved by JSON-LD keyword aliasing:

{
  ...,
  "spdx_id": "@id"
}

but how to simultaneously

alias the property,
and define things like @type and @context for it?

Gregg Kellogg · Accepted Answer · 2022-01-29 18:58:55Z

2

What you want to do is remove the @vocab definition within license, alias spdx_id to @id, and remove the default vocabulary. This treats the object value of license as a node object (really node reference) as all keys other than spdx_id are ignored. See playground link here.

{
  "@context": {
    "@base": "https://octadocs.io/github/",
    "@vocab": "https://octadocs.io/github/",
    "license": {
      "@context": {
        "@vocab": null,
        "spdx_id": "@id"
      }
    }
  },
  "@id": "https://github.com/octadocs/octadocs",
  "license": {
    "key": "mit",
    "name": "MIT License",
    "spdx_id": "MIT",
    "url": "https://api.github.com/licenses/mit",
    "node_id": "MDc6TGljZW5zZTEz"
  }
}

answered Jan 29, 2022 at 18:58

Gregg Kellogg

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2 Comments

Anatoly Scherbakov Over a year ago

Thank you! I did not think to use nested @context here. But I am still a little bit puzzled. How could I specify that the @base for spdx_id (not for other keys in license block) is spdx.org/licenses? Otherwise, this key maps to octadocs.io/github/MIT.

Anatoly Scherbakov Over a year ago

After some thought... It seems okay to add "@base": "http://spdx.org/licenses/" to the nested context and it works, not causing any unwanted side effects. Thanks a lot again!

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