<?xml version="1.0" encoding="UTF-8"?>

  <!ELEMENT bids      (bid_tuple*)>
  <!ELEMENT bid_tuple (userid, itemno, bid, bid_date)>
  <!ELEMENT userid    (#PCDATA)>
  <!ELEMENT itemno    (#PCDATA)>
  <!ELEMENT bid       (#PCDATA)>
  <!ELEMENT bid_date  (#PCDATA)>