Designing XML Schemas such that elements and attributes aren’t typed, data is typed

Hi Folks,

In many programming languages variables are assigned a type. In Common Lisp, on the other hand, variables can hold any values, it is the data objects that are typed:

It is important to note that in Lisp it is data objects that are typed,
not variables. Any variable can have any Lisp object as its value. [Steel]

XML Schemas seem to mirror the former (variables are typed): elements and attributes are assigned a type. For example, this Altitude element is assigned the integer type:

                <element name="Altitude" type="integer" />

Suppose I wanted to create XML Schemas which mirrored the Common Lisp approach: elements and attributes can hold any values, data is typed. How would such schemas be constructed? Would (could) such schemas yield different/unique/interesting validation capabilities?
/Roger