On 6 Apr, 21:01, Spike <fau... (AT) gmail (DOT) com> wrote:

Yes, because the role in which a picture "belongs" to a user and a
gallery "belongs" to a user is likely to be entirely different, thus
not modelled through this transitive relation.

If pictures are shareable by galleries, but pictures only "belong" to
a single user, then I can only assume from this that "belong" here
means some sort of creator or IP owner role. That's sensible, but
quite different from the "inclusion in a set" role with galleries.

On the whole, I'd suggest ignoring the database model for the moment
and focussing on image metadata, probably beginning with a look at
Dublin Core. Once you have a clearer metadata model in your mind, you
can think about RDBMS schema to represent it.