anchor.diff:  // ----------------------------------------
   
   occi_header:
  -    category_header
  +  ( category_header
     | link_header
     | attribute_header
     | location_header
  +  )+
   ;
   
   // ----------------------------------------
  
positive.code:       attributes="occi.storage.size occi.storage.state";
        actions="http://schemas.ogf.org/occi/infrastructure/storage/action#resize ...";
  */
  
  category_header:
    CATEGORY_HEADER term scheme class (title | rel | location | attributes)*
  ;
  
  term:
    TOKEN
  ;
  
negative.code:   action-uri       = URL "?" "action=" term
  */
  //TODO action links spec
  //TODO allow for multiple links per line seperated by ','
  link_header:
    LINK_HEADER  link_path rel (self | link_category)* attributes_attr?
  ;
  