Nick Bart - 2013-02-04

If there is exactly one <relatedItem type="host"> element of an element of <genre authority="marcgt">book</genre>, currently there is no way to distinguish between multivolume monograph or series, i.e., whether this was mapped from a biblatex "maintitle" or "series" field.

Thus, <relatedItem type="host"> elements require disambiguation, and I’d still suggest doing this by including <genre authority="marcgt">multivolume monograph</genre> or <genre authority="marcgt">series</genre>.