4.7.1 Direct Element Constructors

Norm / rule (1|2|3)
    The symbol 'ElementContent' is not defined.

    In rules 1 and 2, change it to 'ElementContentUnit' to agree with the
    prose. In rule 3, change it to 'DirElemContent' to match the grammar.
    But in the RHS of rule 3, instead of
        [[ ElementContent* ]]_ElementContent
    or
        [[ DirElemContent* ]]_ElementContent
    make it
        [[ [[ DirElemContent* ]]_PartitionIntoUnits ]]_ElementContent
    where []_PartitionIntoUnits (or whatever) is responsible for
    restructuring DirElemContent* into ElementContentUnit*.

        [Formal] ElementContentUnit ::= DirectConstructor
                                        | EnclosedExpr
                                        | DirCharsUnit (or whatever)
        [Formal] DirCharsUnit ::= ( [all the possibilities] )+

    You wouldn't need to define []_PartitionIntoUnits formally (you can't,
    really, with only the mapping rule formalism), but it's a bit of
    notation on which you can hang a prose definition.

Norm / rule 5
'(Char | "{{" | "}}" | CharRef | PredefinedEntityRef)+'
    Change this to "DirCharsUnit".