I have been working with Drupal for a wile and was a big pleasure.
Finally I found the project and time to build a multisite installation but when I started to reflect about what tables to share, except of http://drupal.org/node/22754 I didn't find much information about drupal's tables so I did my own documentation.
It's not very much precise, but hopefully enough to get an idea of the whole picture.
I will post it as .ods or .xls files (easier to sort) as soon as I finish reinstalling my testing server, but until then, here you have an standard CSV that you can import in your favorite spreadsheet application:
"TABLE","MODULE","CORE","DESCRIPTION","MULTISITE (if you want different sites with same/shared...)","If shared, requires to share the following “packs”... (underconstruction)","Scenario 1: Single sign on","Scenario 2: Content base","Scenario 3: Multilang interface","Scenario 4:
My research groups","x = shared
o = optional
NEVER... is NEVER :-)"
"access","user","x","User's access privileges","Users",,"x",,,,"access"
"accesslog","statistics","x","User's access registering","Statistics",,,,,,"accesslog"
"actions","actions",,"Node related actions","Actions",,,,,"x","actions"
"actions_registry","actions",,"Node related actions registering","Watchdog",,,,,"x","actions_registry"