Primary keys in nested dataset

A main issue I had to solve, so that I could cover cases of nested datasets (with nesting level >2) was how to handle primary key values if it belongs to nested dataset. Client datasets consider two nested datasets of the same "depth level" to be different and this means that for example values 1,2,3 of one nested dataset and 1,2,3 of another represent different records of the detail table (in back-end database). Of course, under normal circumstances this is not a problem since these values are temporary and are replaced by a permanent value from the database back-end.
However, this was a major problem related to use of these values in my components as primary key values referenced by some foreign keys of another Cds (not belonging to this Delta Tree). I had to implement custom Autoincrement (decrement) behavior of these primary keys, so that values they take are unique among all nested datasets of the same "depth". This made applying updates also safer (using my custom solution) and building complicated file based apps (with many CDSs relating to each other) feasible