XML Schemas and Database schemas

Hi,all
That's clear that XML Schema is supposed to be a perfect way to describe a
data model
of any level of complexity.But that's completely unclear how this perfect
representation, 
generally, could produce the appropriate storage schema for all existing
industrial databases, 
most of which are relative,i.e 2-D -type and ,hence,hardly programmable as
multi-dimensional and
flexible-extensible. Does this mean that XML wave should sweep such class of
databases out
in the future and replace them onto hierarchical and extensible ones at
least in those fields
where XML is supposed to take prevailed place ? 
 
Thanks.
Dmitry