There are inheritance modules for Class::DBI and Tangram, but I haven't seen any for Rose::DB::Object or DBIx::Class. It's a relatively easy thing to build though, just making classes for each type. The only tricky part is turning Documents into Reports, which I've implemented in my own Class::DBI stuff before by having the base class look at a type column and then instantiate an object of the right class with the current primary key.
The rest of the stuff is standard issue ORM functionality that all the Perl ones have.
