I'm working on an implementation of the MIX NISO standard in xml.
I'm confused by an apparent mismatch between the data dictionary http://www.niso.org/standards/resources/Z39_87_trial_use.pdf
and the MIX documentation
While a number of elements are 'Mandatory' in the Dictionary (e.g. CompressionScheme)
All elements are minoccurs=”0” in the Schema (i.e. Optional)
Any feedback gratefully received