>>Hi Michel here goes my opinion
>>On scenario 2 / 4 I will use COMRETURNERROR since I whant to state that an exception has occurred e.g. validation failed or an error as occured the explanation message is what you put on the comreturnerror.
>>On scenario 3 I will return an empty string since everything is OK but no data has match my criteria.
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>Good for point 2 and 4.
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>As for point 3, this will then force the client to implement the logic of verifying for an empty string before converting to a cursor. But, for that one, it is as good as the other approach. I was mostly looking for point 2 and 4. Thanks

Michel about point 3 if the client don't implement the check for empty he will get an error when trying to do an XMLTOCURSOR in this case the error routine will enter in the game.