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• Applythemethodologyasaguidelineforconversiontonextgenerationdata-
base.
As database technology continues to evolve, people will discover
the limitations of relational databases, and will look for the next
generation databases on the market. To convert a relational
database system to the next generation database system is not an
easy task. However, we can make use of the techniques in this
topic as a guideline.
In conclusion, this topic provides an alternative approach for a conversion meth-
odology that is practical enough to be applied. Even though many problems have
been resolved in database conversion, the difficulty arises in the translation of se-
mantics. Neither do we know whether there is a 1:1 or a 1:n relationship between
the parent (owner) and the child (member) segments (records) in the hierarchical or
network schema, nor we can obtain an unique key transformation. The assumption
is that they are all either partially internally identified if the record key exists, or
internally unidentified if the record key does not exist. This assumption is based on
the data structure inherent in the hierarchical or network database where database
navigation is needed to retrieve a target record (segment). This implicit constraint
is a result of the default assumption of partially internally identified or internally
unidentified types that do not apply to relational databases. Therefore, the semantics
of the translated relational database may not be correct. There is a possibility that
the existing record (segment) key itself is unique and therefore a fully internally
identified record (segment).
The complication in semantic analysis appears not only in the DDL of the sche-
ma, but also in the database programs. The major weakness of this methodology is
that it cannot translate directly a low-level hierarchical or network database pro-
gram DML to a high-level relational database program DML by decompilation.
The automation of the direct translation from procedural (with database navigation)
nonrelational DML statement to nonprocedural (without database navigation) rela-
tional DML statement (e.g., SQL) is still a classical problem in computer science.
Application programmers wrote programs based on the conditions and assumptions
that they had about the nonrelational database. These conditions and assumptions
may not be well documented. If we decompile them to a higher level nonprocedural
language such as SQL, the outcome will be variable and it will be difficult to prove
its correctness.
10.2
Application of the Integration of Database and
Expert Systems
The integration of database systems and expert systems forms an expert database
system that combines several different technologies and perspectives. Our meth-
odology for developing such systems by reengineering existing database systems
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