FIXME: TBD.

These elements contain line: dialogue, drama, linegroup, poetry.

The following elements occur in line: text, abbrev, acronym, alt, anchor, author, biblioref, citation, citebiblioid, citetitle, coref, date, editor, email, emphasis (db._emphasis), emphasis (db.emphasis), firstterm (db._firstterm), firstterm (db.firstterm), footnote, footnoteref, foreignphrase (db._foreignphrase), foreignphrase (db.foreignphrase), glossterm (db._glossterm), glossterm (db.glossterm), indexterm (db.indexterm.endofrange), indexterm (db.indexterm.singular), indexterm (db.indexterm.startofrange), inlineequation, inlinemediaobject, jobtitle, link, literal, olink, optional, org, orgname, person, personname, phrase (db._phrase), phrase (db.phrase), productname, productnumber, quote (db._quote), quote (db.quote), remark, subscript, superscript, termdef, trademark, uri, wordasword, xref.