View Management System in Object_Oriented Databases

• Main Authors: Cheng_Pen Wu, 吳正本
• Other Authors: Baw_Jhiune Liu & Joung_Choung Houng
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/27031497528344028749

碩士 === 國立中央大學 === 資訊及電子工程研究所 === 82 === Althohgh there are many researches on the design and manufacture of view management systems in OODB in recent years, many difficulties still exist. This paper aims at designing a view management system in OODB : AMV(Advanced MultiView), and tries to solve the problems other existent systems often encounter. There are four major problems : (1) How can the system integrate the new virtual class defined by view definers into the class hierarchy of the database ? How can this integration be done by the system automatically to avert the data inconsistency due to users' neglect? (2) How can these views be reused to a large extent? (3) How do these operators designed for define views operate on the whole class hierarchy but not just a single class? (4) How can we reduce the system load when creating views? For the purpose of simplifying the definition and management of views, we divede the view creating process into four phases : (1) deriving virtual class phases, (2) integrating global schema phase, (3) selecting view class phase, (4) creating view schema phase. AMV has been implemented successfully in ONTOS OODBMS. By the time of implementation,we divede the view system architecture into four levels : Meta_Schema Level, Physical_Schema Level, Logical_Schema Level, and Objects Level. The first two are the physical database, that explain the real saving status of data in the database. The last two levells are the logical database whose logical status can be seen by users. Through the system level separation, the system can be unbrudened of the heavy load of the view structure reorganization. The design and implementation methods of view management system in AMV are simple and common. We need neither the expansion of traditional object_oriented concepts, nor the special functions offered by DBMS. AMV can be transplanted easily to other well-developed OODB.