we must distinguish between a record type and a instance of the data-item types and record types stored in a database the term subschema refers to an collocation programmer「s vies of the data he uses.
this artical is mainly expatiate on the process how foregrounding subschema been designed and run.
本文主要阐述前台管理子模块的设计与实现过程。
a subschema is a description of only that portion of the database pertinent to a particular user」s needs.
子模式仅仅是数据库中与一个特殊用户的需求相关的一部分的描述。
digraph will be constructed by using the dependence of the left of subset「s fd. some nodes will help to decompose a subschema of bcnf. the key of the subschema is the left or left」s equivalence.