Folks have not-so-positive experience with the LibO/OOO default bibliography database, what with it being effectively either of HSQLDB or CSV text type, for one. One would want to have more choice as to the database type, and to have it storaged more effectively, and in single file, preferrably. Also, there are many popular tools for other database engines, and HSQLDB seems somewhat isolated in this aspect, restricted to all-Java projects, too.
E.g., you might want to have two sets...