Ludovic Courtès <ludo@gnu.org> writes:

> Alternately, you can inspect the ‘%desktop-services’ variable at the REPL:
>
> --8<---------------cut here---------------start------------->8---
> $ guile
> GNU Guile 2.2.3
> Copyright (C) 1995-2017 Free Software Foundation, Inc.
>
> Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
> This program is free software, and you are welcome to redistribute it
> under certain conditions; type `,show c' for details.
>
> Enter `,help' for help.
> scheme@(guile-user)> ,use(gnu services desktop)
> scheme@(guile-user)> ,use(gnu services)
> scheme@(guile-user)> (map (compose service-type-name service-kind) %desktop-services)
> $1 = (slim screen-locker screen-locker mtp network-manager wpa-supplicant avahi udisks upower accountsservice colord geoclue polkit elogind dbus ntp login console-fonts agetty mingetty mingetty mingetty mingetty mingetty mingetty static-networking syslog urandom-seed guix nscd udev special-files)
> --8<---------------cut here---------------end--------------->8---

This is exactly what I was looking for.  Thanks!

-- 
Pierre Neidhardt