Ok. In AX2009, data from a table cannot be directly exported via XML, you need a special intermediary class called
AxYourTableName. Only the fields represented by the
parmYourFieldName methods may be exported.
For a simple example, take a look at \Classes\AxCustGroup
AFAIK, the AIF class wizard is able to generate an Ax-Class automatically.
See
http://msdn.microsoft.com/en-us/library/aa873749.aspx
By the way, an AX-class with an AXD-class are still not sufficient. You additionally need an AXD-query, which is pretty easy to build.