>
>Is it reasonable to use XML data island bound controls for data entry ?
>Are there any samples about this ?

While I have seen/used data islands for binding to controls, I have not seen it used for validating or enforcing data entry.

Check out these two articles at devx for examples: http://gethelp.devx.com/techtips/dhtml_pro/10min/10min0501/td051501-1.asp and http://gethelp.devx.com/techtips/dhtml_pro/10min/10min0701/td070201-1.asp