{
  "@context": {
    "@base": "http://example.org/",
    "@vocab": "http://example.org/vocab/",
    "at": {"@reverse": "@"},
    "foo.bar": {"@reverse": "@foo.bar"}
  },
  "@id": "foo",
  "at": {"@id": "allowed"},
  "foo.bar": {"@id": "allowed"}
}