支持非第一范式的DBMS中DD的设计和实现

Design and Implementation of DD in DBMS for Supporting NF^2

NFMDB数据库管理系统是在 RDBMS的基础上扩充而成的 ,它支持非第一范式 NF2 (Nonfirst normal form)及多媒体数据类型。首先 ,分析了集中式和分离式字典系统的特点 ,并阐述了主动 DD和被动 DD的区别 ;其次 ,讨论了 NFMDB系统为处理 NF2问题而引入的关系字典、属性字典等字典的构造 ,并给出了部分结构描述 ;然后 ,用 create语句描述了一个关于 NF2 存储模式实例 ,同时以 select语句为例讨论了用关系字典和属性字典为基础转换多维 NF2 问题为平滑关系的算法 ,所有这些操作均在关系字典和属性字典中给出了相应的存储描述 ;最后 ,探讨了以关系方式存储 DD的优点以及 DD与 DBMS的关系。由此得出以扩充 DD系统为基础处理 NF2 问题是可行的。

The database management system NFMDB is extended on the basis of RDBMS. It supports NF 2 and multimedia data type. In this paper, firstly, we discuss the IDS, the SDS, the active and the passive dictionaries. Secondly, we discuss the relation dictionary, the attribute dictionary and the others, all of which are used for NF 2, and their structural descriptions are partly given out. Thirdly, we use the create statement as an example to describe the storage schema of NF 2 and at the same time we use the select statement to discuss emphatically the algorithms, with which NF 2 of multiple dimensions is transferred into the flat relation. All these operations are described in the relation dictionary and the attribute dictionary. Lastly, we discuss the virtue that DD is stored with the relation between DD and DBMS. Then we can draw a conclusion that NF 2 can be processed with the extended DD system.