拍卖过程
委托（委托人、物品信息、可提出保留价）
指定竞价拍卖的商品
多次竞价
成交或流排（获得拍卖结果）
设计监控程序
限制：竞价前必须指定拍卖物品；
限制：不同物品的竟价不可交叉进行(The auction process
Entrustment (client, goods information, may offer reserve price)
Specify the goods to be auctioned
For many times
Transaction or flow row (obtaining auction results)
Design monitor
Limit: the auction items must be specified before bidding.
Limit: the price of different items should not be crossed)