Pseudo-Algorithm for ValidQuote
Get the Quote and Quote Item business component. Create a variable invalidFlag=N.
For each record in the Quote Item business component, check the Base Price field:
If this field is empty, set invalidFlag = Y and set the Invalid Flag field = Y for that record.
Set the Invalid output argument = invalidFlag.
Set the Error Message output argument if there is any error;
If Return Error Code = N, do not return an error;
Else return an error.