shapes-ISSUE-57 (labra): Grouping of Shapes [SHACL Spec]

shapes-ISSUE-57 (labra): Grouping of Shapes [SHACL Spec]

http://www.w3.org/2014/data-shapes/track/issues/57

Raised by: Jose Emilio Labra Gayo
On product: SHACL Spec

When combining Shapes with and and or operators, it is natural to group those shapes. In compact syntax, grouping is represented by parenthesis. 

For example:

<PersonShape> {
  foaf:name xsd:string
| ( foaf:firstName xsd:string +
  , foaf:lastName xsd:String
  )
}

A natural extension is to add cardinalities on those groups. SHACL spec should define if groupings and cardinalities over groupings are possible.