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of integrating them, we can perform a methodology of converting a hierarchical or
network database into a relational database. Our approach is to translate schema
from hierarchical or network to relational in the first phase. We can then provide a
relational interface in the second phase by imposing secondary indices in the hierar-
chical database schema and data. A software layer is developed for emulating SQL
statements to hierarchical or network database DML statements. As a result, the
users can run an embedded SQL program using a hierarchical or network DBMS.
The objective is to let users write new programs using SQL and phasing out the hi-
erarchical or network database programs as a temporary solution. As all the obsolete
hierarchical or network databases are rewritten or deleted, we can then perform the
third phase of data conversion from hierarchical or network database to relational
database as a permanent solution of database conversion (migration). In converting
a relational database into an object-oriented database, we suggest using a frame
model metadata to implement an object-oriented interface to a relational database to
allow user using OSQL to access a relational database. The frame model metadata
allows users to specify data operation into its method class for encapsulation.
Questions
Question 6.1
What is inheritance and what is encapsulation in an object-oriented database? How
can these two features be implemented in a relational database? What are the major
differences in the level of hidden operations (automation) of using these two fea-
tures in an object-oriented database and in a relational database?
Question 6.2
What is a frame model metadata and how it can be used in converting a relational
database into an object-oriented database?
References
Fong J (1993) A methodology for providing a relational interface to access hierarchical or network
database, Ph.D. Thesis, University of Sunderland
Fong J (2002) Translating object-oriented database transactions into relational translations. Inf
Softw Technol 44(1):41-51
Fong J, Cheung J (2001) Translating OODB method to RDB routine. Int J Softw Eng Knowl Eng
11(3):1-27
Fong J, Ng W, Cheung SK, Au I (2006) Positioning-based query translation between SQL and
XQL with location counter, lecture notes in computer science, 3842, pp 11-18
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