XSD spec question

In section 3.14.2 of http://www.w3.org/TR/xmlschema-1/ it says "{any  
attributes with non-schema namespace . . . }" Does that mean I can  
add my own attributes? For example can I do this:

  <simpleType name="myName" xyz:myattribute="something">
   . . .
  </simpleType>