ORA-FO-TRANSLATE 7.4.14: fn:translate

*Functions and Operators, Section 7.4.14: fn:translate* says that the 
result is the empty sequence if $transstring or $mapstring is the empty 
sequence. This is not intuitive.

If $mapstring is the empty sequence, then the result should be $srcval.

If $transstring is the empty sequence, then the result should be
either
    $srcval
or
    $srcval minus the characters in $mapstring
[either definition would make sense].