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 (_:S1) .
_:S1 a sx:ShapeDecl ; sx:shapeExpr [ a sx:Shape ;
sx:expression [ a sx:TripleConstraint ;
sx:predicate <http://a.example/p1> ] ] .