Duplicate USING prefix encountered.
#2508 Compile-time warning
Duplicate USING prefix encountered.
Additional Information
The 'X' 'Y' already appears in the current list of USING
prefixes.
where X is attribute, counter,
elements,
referent,
stream, or
switch and Y is the object's name.
or
The term 'NESTED-REFERENTS' already appears in the current list of USING prefixes.
Recovery
Compilation continues normally.
Explanation
Each object may appear at most once in any consecutive list of
using prefixes.