How to get a list of all installed OS X System Services?

Question

I'm writing an Automator plugin for OS X that lets you invoke any System Service.

I like to offer a complete list of all available Services to the user, so that he doesn't have to enter their names manually.

Is there an API function that lets me get all the Services? After all, OS X can list the services in the menu, so how does it get this list?

Clarification. I mean these Services:

Answer 1

Run following command "pbs -dump" or it's derivates. Also disassembly of this file can tell you a lot "/System/Library/CoreServices/pbs"

Alternative to fetch services is to read:

~/Library/Caches/com.apple.nsservicescache.plist