8. optional part

Is set if: For the current root-element an optional part exists.

Effect if set: For the current root-element an optional part exists (see section 21.2.9 on page ) and the offset, at which byte it starts in the root-element.

If not set: For the current root-element no optional part exists (maybe because it was not stored to save space).

Effect if not set: No offset is given for the optional part in the current root-element and no optional part is given in the current root-element.