Within the reference model, there are several structural
attributes which are coded from a specified vocabulary. In some
cases, such as 'territory', 'language', and 'mime type', the
vocabulary is really just a list of codes - there are no rubrics,
and no idea of translation (i.e. within computer systems, 'jp', the
country code of Japan is 'jp' in all languages, including
japanese). These codes can be expressed in the model directly
using CODE_PHRASEs. Any attribute which is not the name of
something in the real world, but is either an acronym (e.g. "RSA")
or a self-defining word (e.g. "gzip") is in this category.

However, other structural (predefined) attributes should be
expressed as proper coded texts. Examples include
RELATED_PARY.relationship, PARTICIPATION.mode, and any other term
which should be viewable in the user interface in the local
language.

Currently these guidelines are not followed properly: there are a
number of structural coded attributes which are expressed as a
bare CODE_PHRASE, when a DV_CODED_TEXT should be used.

Another problem is that the location of the attributes for
language and charset on DV_TEXT probably is not optimal. No-one
has a use case in which language could vary at any finer level
than Entry (since Entries are the minimum indivisible unit of
information in openEHR); it may not even be necessary to record
charset at all, if we assume Unicode UTF-8. If we assume unicode,
but the byte encoding can vary from UTF-8 to UTF-16, which could
be the case for EHRs in the US versus EHRs in China, then we still
do need to record which encoding it is.

The current list of 'structural' attributes is as follows. Starred
items are code only attributes:

*DV_TEXT.language
*DV_TEXT.charset
DV_QUANTITY.property
*DV_MULTIMEDIA.media_type
*DV_MULTIMEDIA.compression_algorithm
*DV_MULTIMEDIA.integrity_check_algorithm
TERM_MAPPING.purpose
*DV_ENCAPSULATED.charset
*DV_ENCAPSULATED.language

ATTESTATION.status
PARTICIPATION.mode
RELATED_PARTY.relationship
VERSION_AUDIT.change_type
FEEDER_AUDIT.change_type

*COMPOSITION.territory
EVENT_CONTEXT.setting
ELEMENT.null_flavour