anchor.diff:  // ----------------------------------------
   
   occi_header:
  -  ( category_header
  +  (
  +    multiple_category_header
  +  | category_header
  +
  +  | multiple_link_header
     | link_header
  +
     | attribute_header
  +
     | location_header
     )+
     EOF
  
positive.code:   X-OCCI-Location: http://example.com/compute/123
    X-OCCI-Location: http://example.com/compute/123, http://example.com/compute/123
  */
  
  location_header:
    LOCATION_HEADER location_paths
  ;
  location_paths:
    location_path (',' location_path)*
  ;
  location_path:
    PATH
  
negative.code:   X-OCCI-Attribute: occi.compute.architechture="x86_64"
    X-OCCI-Attribute: occi.compute.architechture="x86_64", occi.compute.cores=2
  */
  //TODO output attribute header as JSON
  attribute_header:
    ATTR_HEADER attribute_attrs
  ;
  attribute_attrs:
    attribute_attr (COMMA attribute_attr)*
  ;
  
  // ----------------------------------------
  