Datacage: Introduced <dc:virtual-column name="colname" type="type" expr="XPath"> dc:virtual-column can be used to virtual add or replace a column named 'colname' to the current result set. The value is determined by evaluating "XPath", the type is determined by "type" (possible values: number, bool, node, nodeset, string. defaults to string). Usage: <dc:virtual-column name="c" type="number" expr="$a+$b"> <dc:for-each> <dc:message>{$a} + {$b} = {$c}</dc:message> </dc:for-each> </dc:virtual-column> table a | b --+-- 1 | 2 3 | 4 will result in: 1 + 2 = 3 3 + 4 = 7

- Validation of the input values of an incoming feed() call