{
  "@context": "http://www.w3.org/ns/shex.jsonld",
  "type": "Schema",
  "shapes": [
    { "type": "ShapeDecl",
      "id": "http://a.example/S1",
      "shapeExpr": {
        "type": "Shape",
        "expression": {
          "type": "TripleConstraint",
          "predicate": "http://a.example/p1"
        }
      } },
    { "type": "ShapeDecl",
      "id": "http://a.example/S2",
      "shapeExpr": {
        "type": "Shape",
        "extends": [ "http://a.example/S1" ]
      } }
  ]
}