I'll mention EDB, emacs data base, here, even though I haven't used it for
several years.

http://gnuvola.org/software/edb/

It's available on many GNU/Linux distros, as a package.  It is for Gentoo,
and perhaps for Debian/Ubuntu as well.

It is extensible/programmable, so that various interfaces could perhaps be
possible.  I spent a little time years ago setting up an Addresses database,
with output formats to automatically set up a LaTeX header for each marked
address.  It was a bit klunky, to be sure, but it worked REALLY well, and it
worked the way I wanted it to.

It's an old piece of software.  I tried it lately with my address DB, with
Emacs 23, so it may just still work fine.

In the examples directory, above, are a rolodex database, possibly somewhat
similar to what I had going, and some other examples.   There has been some
relatively recent effort into maintaining EDB.

I write this not as a programmer, but a user, just to point to something
that has worked well for me in the past.

Alan Davis