| Summary: | 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.
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