This is an open question. We will need during the review of stabilizing Efl.Model interface to evaluate what is a sane value for the index range. At the moment we have a mix of int, unsigned int and uint64. I am leaning more toward uint64 as this is fully future proof. uint32 is kind of next down on the list. I would think that a UI trying to show a uint32 sizedd list/grid might have some issue :-) So this is kind of a larger discussion to have.
I'm little bit worry about 32 bit system needs in the future on tizen side,
but currently it seems we all uisng 64 bit system and it won't be a problem.
I've recently faced some signed-unsigned default datatype issue on char,
so using strict datatype could be nicer to avoid such problem.
lets to discuss again on this matter after all infrastructure is ready :)