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