Intended behaviour of relative scoped @base

[Pritz96]

Hi, I have a question about what the intended behaviour of a relative scoped @base should be and why different parsers treat them differently.

Take the JSON-LD below:

{
    "@context": {
        "@base": "http://global-base/",
        "options": {
            "@type": "@id",
            "@id": "http://example.com/option",
            "@context": {
                "@base": "Test/"
            }
        }
    },
    "@id": "http://example.com/1",
    "@type": "ExampleClass",
    "options": [{
        "@id": "Documents/Pictures"
    }]
}

Using the JSON-LD Playground this JSON-LD expands to:

[
  {
    "@id": "http://example.com/1",
    "@type": [
      "http://global-base/ExampleClass"
    ],
    "http://example.com/option": [
      {
        "@id": "http://global-base/Test/Test/Documents/Pictures"
      }
    ]
  }
]

Notice that the uri of the option is http://global-base/Test/Test/Documents/Pictures (the path contains Test twice however I was expecting the path to be http://global-base/Test/Documents/Pictures (I thought the scoped relative base would be relative to the global base). If I change the relative base to become an absolute base then I get the desired uri when expanded but I'm confused as to why the relative @base duplicates Test.

A related question I have is why does rdflib parse this JSON-LD differently to json-ld playground/pyld

When I serialise with rdflib I get the following output (Test only appears once in the option uri):

[
  {
    "@id": "http://example.com/1",
    "@type": [
      "http://global-base/ExampleClass"
    ],
    "http://example.com/option": [
      {
        "@id": "http://global-base/Test/Documents/Pictures"
      }
    ]
  }
]

When I serialise with either JSONLD Playground or pyld (Test appears twice in the option uri):

[
  {
    "@id": "http://example.com/1",
    "@type": [
      "http://global-base/ExampleClass"
    ],
    "http://example.com/option": [
      {
        "@id": "http://global-base/Test/Test/Documents/Pictures"
      }
    ]
  }
]

Can anyone shed some light on this, thank you.