xsd:appinfo for formal semantics in XSD

At times we have talked about embedding formally-expressed semantics
in <xsd:annotation>.

On a call I was on recently, one of the mavens there gently
suggested that we might better put this in <xsd:appinfo>.

For more, see for example

http://www.w3.org/2005/06/21-xsd-user-minutes.html

Al