Hi,
Or in other words, do we have two different notions here? Tags and rolls? Or only one with roll being a special case of tag.
and
It seems to me stacking has a different purpose, namely to offer the possibility to see only one of many similar pictures, typically in the case of burst shots. Though of course, stacking and grouping are not completely unrelated.
I wrote a loooong mail about this but then I figure I'd spare everyone my mental ramblings. Basically yes, grouping and stacking are similar things. And grouping and stacking can be implemented with tags. As can versions. It will be a bit cludgy and it will require some "hacks" in order to make it work however. So because of that (and to save the sanity of future developers of the project) I think it would be better to use a clean OO design and add groups as a "proper" member of the F-Spot design. /Marcus