how to enforce xmlforest creat elements even if expression value is null

[loserboy]

I would like to use the oracle XMLFOREST fonction. (Link for definition)Example Syntax:\[quote\] XMLFOREST( [value expression AS alias], [...])\[/quote\]My problem is that if value expression is NULL, then no element is created for that value expression.How can i enforce it to add empty XML fragment?Thanks for your help.