实体bean的关联

Question

anybody来说说？另外，在一个例子中，有ejb-jar.xml配置文件里有实体bean(BnUser和BnRole)的关系如下：
     <ejb-relation >
         <ejb-relation-name>Roles</ejb-relation-name>         <ejb-relationship-role >
            <ejb-relationship-role-name>has-role</ejb-relationship-role-name>
            <multiplicity>Many</multiplicity>
            <relationship-role-source >
               <ejb-name>BnUser</ejb-name>
            </relationship-role-source>
            <cmr-field >
               <cmr-field-name>bnRoles</cmr-field-name>
               <cmr-field-type>java.util.Collection</cmr-field-type>
            </cmr-field>
         </ejb-relationship-role>         <ejb-relationship-role >
            <ejb-relationship-role-name>is-role-of</ejb-relationship-role-name>
            <multiplicity>Many</multiplicity>
            <relationship-role-source >
               <ejb-name>BnRole</ejb-name>
            </relationship-role-source>
            <cmr-field >
               <cmr-field-name>bnUsers</cmr-field-name>
               <cmr-field-type>java.util.Collection</cmr-field-type>
            </cmr-field>
         </ejb-relationship-role>      </ejb-relation>这里两个实体bean(BnUser和BnRole)的关系为“多对多 ”，但我没找到一个“连接表”（或说一个“连接bean”）分解这个多对多关系为两个“一对多”关系，怎么回事?多对多关系不一定要分解成两个一对多关系的？