It was in that spirit that the UCP were first introduced - to alleviate the confusion caused by individual countries promoting their own national rules on letter of credit practice.
请教老师：介词by后句子成份剖析。
过去分词表示被动意义，其逻辑上的施事者（即动作的发出者）由介词by引出。在大的方面，by介词短语是方法状语（方法、渠道、工具、施事者等）中的施事者状语（夸克的看法）。