OBJECT-BASED DATA MODEL: PRINCIPLES AND COMPONENTS - Database Design and Development: An Essential Guide for IT Professionals - page 201

FcltyName

FacilityNo FcltyCountry

ProdLineNo

ProdLnDesc

PRODUCTION
FACILITY

PRODUCT
LINE

1

LineType 1

contains

ProdName

PlNo ProdNo

ModelNo

*

*

PRODUCTION
LINE

makes PRODUCT

*

*

1

1

LineName

1

1

PRODUCT
UNIT

includes

operates

PartNo

*

*

ActivityID

SerialNo

LINE
ACTIVITY

*

ASSEMBLY
PART

Color

contains

*

ActvtyDesc

ActvtyType

Quantity

Figure 6-28 Data model diagram: manufacturing operations.

• With just these components, you can represent any collection of real-world
information in the data model.
• Some object sets are subsets of other object sets. Generalization/specialization
deals with supersets and subsets. Subsets inherit attributes and relationships
from a superset.
• Physical objects represent physical things that can be seen or touched, for
example, a copy of a book; conceptual objects indicate nontangible things, for
example, “book.”
• In a recursive relationship, instances of an object are associated with other
instances of the same object.

REVIEW QUESTIONS

1. Explain how an object-based data model is a generic data model.
2. Name the components of the object-based data model and list the standard
symbols or notations used to construct the model.
3. Distinguish between object sets and object instances. Give an example.
4. Describe the different types of objects, with an example for each type.
5. What is your understanding of null values for attributes? When are null
values used?
6. “Relationships are really associations between instances of objects.” Explain
this with an example.
7. What do maximum and minimum cardinality indicators represent? What is
an optional relationship?