Confusion regarding @default and @embed in JSON-LD 1.1?

[cboettig]

In this json-ld playground example I believe the 5 @ids for the char property used to be returned given the displayed frame under JSON-LD 1.0 spec, but are dropped under the current spec for reasons I don't entirely understand. I think this has to do with the changed behavior of omitGraph? I am not sure how to update my frame.

I believe the reason has to do with duck typing and the presence of the states property under char in my frame. In this data, I'm not able to declare a specific type for the char object, which can sometimes contain the states property. I need the frame to assert that if it has the states property, it should use "@embed": "@never" so I cannot simply omit that assertion; even though that would in this example allow the char ids to display. I'd greatly appreciate clarification on the possible change in behavior between the spec and the best/right way to address the issue in this example.

[dlongley]

I think this is just a bug in the jsonld.js implementation:

digitalbazaar/jsonld.js#323

I propose we close and fix it over there. If the fix results in any other tests breaking we can raise a new issue.

[gkellogg]

It doesn't match because the Frame Matching Algorithm doesn't match any of the nodes which are a part of "char".

Consider a simplified use case (playground link):

Input:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/vocab#",
    "@version": 1.1
  },
  "characters": {
    "@id": "m3",
    "@type": "ContinuousCells",
    "label": "Continuous characters",
    "format": {
      "char": [
        {
          "@id": "ContinuousCharacter1",
          "label": "this is character 1"
        },
        {
          "@id": "ContinuousCharacter2"
        },
        {
          "@id": "ContinuousCharacter3"
        },
        {
          "@id": "ContinuousCharacter4"
        },
        {
          "@id": "ContinuousCharacter5"
        }
      ]
    }
  }
}

Frame:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/vocab#",
    "@version": 1.1
  },
  "characters": {
    "format": {
      "char": {
        "states": {
          "@default": {}
        }
      }
    }
  }
}

In this case, we have the sub-frame {"states": {"@default": {}}}, with each of the inputs with id "ContinuousCharacter?".

The algorithm matches if it has no properties (it has properties, @id), @type matches (no @type), or any property which isn't a keyword matches (only "ContinuousCharacter1" has a property, so it matches).

To get them to match you would need to add "@id": {} to wildcard match each node having an @id. With the updated frame it should work:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/vocab#",
    "@version": 1.1
  },
  "characters": {
    "format": {
      "char": {
        "@id": {},
        "states": {
          "@default": {}
        }
      }
    }
  }
}

It does work in my implementation, but doesn't in jsonld.js, which is a bug there.

The expected result is:

{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/vocab#",
    "@version": 1.1
  },
  "characters": {
    "@id": "m3",
    "@type": "ContinuousCells",
    "label": "Continuous characters",
    "format": {
      "char": [{
        "@id": "ContinuousCharacter1",
        "label": "this is character 1",
        "states": {}
      }, {
        "@id": "ContinuousCharacter2",
        "states": {}
      }, {
        "@id": "ContinuousCharacter3",
        "states": {}
      }, {
        "@id": "ContinuousCharacter4",
        "states": {}
      }, {
        "@id": "ContinuousCharacter5",
        "states": {}
      }]
    }
  }
}

The matching behavior may be different to that before, but that was never standardized.

[cboettig]

Thanks @gkellogg, that makes sense. The expected result as shown by your implementation looks good!

I had actually tried adding an "@id": {} to char but as you note, no look on the jsonld.js implementation in playground (which is also what I'm using via R).

[cboettig]

@gkellogg I'm still not getting the expected behavior you document in #58 (comment) when I try your example at https://json-ld.org/playground/ . What's the process for #62 to show up in the playground instance?