How to reference a value in the xml instance document

Hi folks, I hope that this question makes sense and that it isn't
trivial. I've searched the web and this list's archive before asking
it but I cannot find any leads. :/

In XML Schema, is it possible to refer to a value in the XML document
for purposes of schema validation?  I know that you could use an
appdata node to call out to some other type of schema validator such
as schematron, but I'm hoping this is possible in pure XML Schema.

An example might be easiest.

good xml doc
<person birthYear="1973" deathYear="2004"/>

bad xml doc
<person birthYear="2004" deathYear="1999"/>

can I write a minInclusive restriction in an XML Schema such that the
schema validates that deathYear is greater than or equal to birthYear?

Thanks for your time,

Daniel Einspanjer