Currently FieldMappings the do use a wildcard are not allowed to be mapped to an target field.
The main reason for this is that things like the following example
that would copy all fields from the dc elements namespace to the dc terms namespace are not implemented.
However copying multiple fields to a single one are already supported but not accepted by the FieldMappings constructor. A possible usage scenario is to collect all references or literal values to create an disambiguation context. See the following listing for an example.
The change is really trivial as one needs only comment the check in the constructor of FieldMapping that explicitly disallows those things.