A GetCodeInfo message implies that the user is passing a name and wants the associated information about that name returned. The category attribute will tell the service what metadata table to search in and does not have to be included. If COLUMN_CD is not included, all tables the user is allowed to access will be searched.
The attributes provide information about the results to be returned. If the number of rows found is greater than max, then an error message will be returned in the i2b2 header. If the max is left out then it is interpreted that there is no max.