This article provides a formalization of the W3C Draft Core SHACL Semantics
specification using Z notation. This formalization exercise has identified a
number of quality issues in the draft. It has also established that the
recursive definitions in the draft are well-founded. Further formal validation
of the draft will require the use of an executable specification technology.Comment: 57 pages, Invited Expert contribution to the W3C RDF Data Shapes
  Working Grou