Attribute Element (Nillable Attributes)
The <attribute> element has an optional nillable attribute that specifies whether FME should interpret an empty element as an empty string attribute (when the nillable attribute is false or missing), or a null attribute (when the nillable attribute is true).
<attribute nillable="false"> <name> <literal expr="my-optional-attribute"/> </name> <value> <extract expr="."/> </value> </attribute>