Database Management System Emulation - Information Systems Reengineering, Integration and Normalization - page 231

Segment TREATMNT

TRTYPE TRDATE MEDITYPE

CHEST PAIN 860823 HEART DRUG

REST 860714 NIL

REST 860514 ZANTAC

BANDAGE 860602 NIL

REST 860603 INFLUENZA

LEG SURGE 860721 NIL

Segment FACILITY

FACTYPE TOTFACIL FACAVAIL

CARDIOGRAPHIC M/C 10 9

X-RAY M/C 3 3

OXYGEN SUPPLY 90 81

CARDIOGRAPHIC M/C 10 9

X-RAY M/C 3 3

OXYGEN SUPPLY 90 81

Phase I. Schema translation.
Step 1. Map hierarchical schema to the EER model.
In this case study, certain substeps are skipped because of the following:

• Therearenoimpliedrelationships(i.e.,noduplicatekeyfieldsinsegments)
• Noalternativerelationshipexists(i.e.,noloopydatabaseaccesspathexists)
• Nounaryorn-aryrelationshipexists(i.e.,therearenocardinalityinsegment
related to itself or more than two segments semantically related to each other)
• Noaggregation,generalization,orcategorizationexists(i.e.,nosuchadvance
semantics exist among the segments)

We can derive entities' relationship by mapping each segment type into a relation
and each parent and child segment relationship into the entities' relationship in the
EER model. We can also derive the entity key by deriving the default partial inter-
nally identifier for each segment type. However, since there is no segment key in
segment type FACILITY, we must specify this segment as internally unidentified.
Also, the users specify segment WARD and segment PATIENT as fully, internally
identified. Figure 6.3 shows the resultant EER model.
Step 2. Map the EER model to the relational schema.