control structure
repeat over specified? attributes (of element-expression)? as alias-name local-scope again
An action that can be used to iterate over all the attributes that are:
repeat over attributes must specify an alias-name following as. This
        name is used to identify the attribute selected for each iteration within the repeat over action.
        Any valid OmniMark name can be used.
      
For example:
repeat over specified attributes as this-one output key of attribute this-one output "='%v(this-one)'%n" again
Use of the keyword attributes followed by  alias-name, without qualifiers, inside
        the repeat over data-attributes action always refers to the attribute identified by the alias.
      
To refer to an attribute of the currently opened element with the same name as the alias-name
        being used, use the element qualifier of element. An element-expression always
        indicates that the attribute belongs to the identified, currently opened element.
      
If a repeat over action in the input processor iterates over a set of attributes or over the
        tokens of an attribute, or if an attribute or attribute token is identified by a using prefix, all
        text written to the #markup-parser stream will be "buffered" in the same manner.