1
It's better for DOJO to make a widget just like "CaseCadingDropDown" in MicroSoft-Asp.net's AjaxToolkit.
We know , we always have to make two "" or more when we want to make "Country-Town-Street-PostCode" select .
So why don't we just make a widigt called "CaseCadingDropDown" like MicroSoft called ?
I think this widigit will be very helpful , I have found so many questions about "How to make FilterSelect dynamic" in this forum.

2
The "ItemFileReadSotre" must be extended.
Right now , I use "FilterSelect" and "ItemFileReadSotre" to make my "CaseCadingDropDown" ,