PREFIX ex: <http://a.example>
PREFIX sx: <http://www.w3.org/ns/shex#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>

[] a sx:Schema ;
    sx:shapes (<http://a.example/S1>) .

<http://a.example/S1> a sx:ShapeDecl ; sx:shapeExpr [ a sx:Shape ;
  sx:expression [
    a sx:TripleConstraint ;
    sx:predicate <http://a.example/p1> ;
    sx:valueExpr [
      a sx:ShapeNot ;
      sx:shapeExpr [
        a sx:NodeConstraint ;
        sx:values ( <http://a.example/v1> <http://a.example/v2> <http://a.example/v3> ) ] ] ] ] .