买家网上购物的用例规约的报告模版，包括用例目标、用例主角、前后置条件、基本/备选事件流、步骤和补充约束、用例间关系和涉众利益的考虑 -Buyers shopping the report of the Statute of the use case template, including the target use case, use-case characters, before and after the set conditions, the basic/alternative fl