On one hand, there's this: "A Boost library *should not* use libraries other than Boost or the C++ Standard Library." (http://www.boost.org/development/reuse.html) On the other hand, sometimes it just seems like common sense. E.g. Boost.Math uses NTL, MPFR, and others. Now I'm trying to get quince and its backend libraries (quince_postgresql, quince_sqlite) into shape for blincubator. The job of the backends is to liaise between quince and other people's libraries: libpq and sqlite3. There is no getting around that. So I was hoping that the prohibition would be waived in this case, as it was in the case of Boost.Math. The trouble I have is that quince_postgresql and quince_sqlite are *not* header-only, and their code that calls libpq and sqlite3 is in .cpp files. And yet I don't want them to break the boost build for people who don't need this stuff, and haven't installed either or both of those third-party libraries. Any suggestions? Any precedents? Thanks, --- Michael