SEMANTIC DATA MODEL TO RELATIONAL DATA MODEL - Database Design and Development: An Essential Guide for IT Professionals - page 275

Object Set OR Entity Type

EMPLOYEE

Relational Notation

EMPLOYEE (Attribute1, Attribute2, Attribute3, Attribute4)

EMPLOYEE relation

Attribute1 Attribute2 Attribute3 Attribute4

.

EMPLOYEE
instances

.

Figure 9-3 Mapping of object set or entity type.

SocSecNo

EmpName

EMPLOYEE

EmpID

EmpAddr

Relational Notation

EMPLOYEE (EmpID, SocSecNo, EmpName, EmpAddr)

EMPLOYEE
relation

EmpID
1234
2345
3456
4567

SocSecNo
101-38-2121
320-55-9641
333-22-1111
123-47-3257

EmpName EmpAddr

Daniel R. Grady 6 William Street, Jamesburg, NJ 08810

Alice M. Knox 1 Bradford Place, Iselin, NJ 08834

Matthew Rader 47 Woods Drive, Edison, NJ 08817

Ramola Ruskin 55 Walker Lane, Metuchen, NJ 08819

Figure 9-4 Mapping of attributes.

Attributes

Objects have intrinsic or inherent characteristics, so naturally, the next component
to be considered is the set of attributes of an object. Figure 9-4 shows the transfor-
mation of attributes.
Make note of the following points with regard to the transformation of attributes:

• The attributes of an object are transformed into the columns of the corre-
sponding relation.
• The names of the attributes become the names of the columns.
• The domain of values of each attribute translates into the domain of values for
the corresponding column.