Contributions • We propose a simple formal language for graph shapes that subsumes both ShEx and SHACL. The semantics of the language is based on the semantics of Datalog, and also equivalently defined in terms of Monadic Second Order Logic with Presburger constraints. • We propose a formal semantics of SHACL as a translation to this language. Thanks to this translation, we show that SHACL can be extended with well-defined stratified recursion. • We show how ShEx can be translated to this language. • We explore the necessary restrictions on ShEx so that it can be translated to SHACL, and also the possible modifications of SHACL so that it can capture a bigger fragment of ShEx
