Design pattern for row-level security?

Has anyone implemented a system that supports row-level security? By
row-level I'm speaking of a system where you could say:

Mike can add comments to items.
Mike can change items.
Mike can NOT access item 12345 in any way (not even read)
Jane can display any item where she is the product-line manager
Jane can not display item 87997 even though she is product-line manager
Pete can edit items where he is buyer
Pete can edit item 99890 (even though he isn't buyer)
Pete can add notes to items where he is seconday buyer, but can't change
them.

Any experience or places to look for decent design patterns?

-Walden

------------
Walden H Leverich III
President
Tech Software
(516) 627-3800 x11
(208) 692-3308 eFax
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com 

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)