In order to convert to and from GIFT Format, we first have to write out a tree to represent the internal format before implementing it.
It's possible that a single tree type can't represent both GIFT and MediaWiki-extensions-Quiz markup formats , in which case we make need two different tree types, and perform operations in between to convert GIFT tree to wiki tree and vice versa.
GIFT format has broader adoption than the MediaWiki-extensions-Quiz markup format, making it the easier of the two to research, document and design. Some more info about GIFT can be found at T24475: GIFT format.