{
  "@context": "http://www.w3.org/ns/shex.jsonld",
  "type": "Schema",
  "shapes": [
    { "type": "ShapeDecl",
    "id": "http://a.example/S",
    "shapeExpr": {
      "type": "Shape",
      "expression": {
        "type": "TripleConstraint",
        "predicate": "http://a.example/p1",
        "valueExpr": "http://a.example/Sext"
      }
    } },
    {
      "id": "http://a.example/Sext",
      "type": "ShapeDecl",
      "shapeExpr": {
        "type": "ShapeExternal"
      }
    }
  ]
}