Data Conversion - Information Systems Reengineering, Integration and Normalization - page 150

The algorithm reads each record occurrence by database navigation. For each record
occurrence of fully internally identified read, it reads its owner record occurrences
from the bottom up to the system owned record types. It then concatenates the
owner record keys for the record type of partially internally identified or internally
unidentified. For owner record keys with record type of fully internally identified,
the concatenation of owner record keys is not required. The objective is to concat-
enate owner record identifiers as foreign keys in the target record when mapped to
the relational database.
Step 3—Transfer sequential files to target computer (optional).
We must transfer the unloaded sequential files into another computer if the target
relational database is residing in a different physical location or another machine.
The data format may need to be changed due to different bit size per word and/or
character size per record. This is a straightforward task for which many software
utilities already exist.
Step 4—Upload sequential files into a relational database.
Finally, we upload the sequential files into a relational database according to
the translated relational schema. The relational schema must be created before the
upload process.

4.5.1 Case Study of Data Conversion from Network to Relational

Before converting data from network to relational, a translated relational schema
must be defined. We apply the previously described method to the university enroll-
ment system for illustration. Figure 4.8 shows a network schema and its database.
The following steps show the different stages in the conversion process:
Step 1—Create a template file to define the network databases and its translated
relational schema:
During the template creation process, the user is prompted to input the record
class of each entity. The following shows the user input for each entity type in the
university enrollment system.

The identify type (F, P, I) of: COURSE# F

The identify type (F, P, I) of PREREQUISITE F

The identify type (F, P, I) of DEPARTMENT F

The identify type (F, P, I) of INSTRUCTOR P

The identify type (F, P, I) of SECTION P

The identify type (F, P, I) of STUDENT F

The identify type (F, P, I) of GRADE P