After studying this chapter, you should be able to:
Concisely define each of the following key terms:
business rule, term, fact, entity-
relationship model (E-R model), entity-relationship diagram (E-R diagram), entity,
entity type, entity instance, strong entity type, weak entity type, identifying
owner, identifying relationship, attribute, required attribute, optional attribute,
composite attribute, simple attribute, multivalued attribute, derived attribute,
identifier, composite identifier, relationship type, relationship instance,
associative entity, degree, unary relationship, binary relationship, ternary
relationship, cardinality constraint, minimum cardinality, maximum cardinality,
State reasons why many system developers and business leaders believe that data
modeling is the most important part of the systems development process with a high
return on investment.
Write good names and definitions for entities, relationships, and attributes.
Distinguish unary, binary, and ternary relationships and give a common example
Model each of the following constructs in an E-R diagram: composite attribute,
multivalued attribute, derived attribute, associative entity, identifying relationship,
and minimum and maximum cardinality constraints.
Draw an E-R diagram to represent common business situations.
Convert a many-to-many relationship to an associative entity type.
Model simple time-dependent data using time stamps and relationships in an
You have already been introduced to modeling data and the entity-relationship
(E-R) data model through simplified examples in Chapter 1. (You may want to
review, for example, the E-R models in Figures 1-3 and 1-4.) In this chapter, we
formalize data modeling based on the powerful concept of business rules and
describe the E-R data model in detail. This chapter begins your journey of learning
how to design and use databases. It is exciting to create information systems that
run organizations and help people do their jobs well.
Our excitement can, of course, lead to mistakes if we are not careful to follow
best practices. When we fail to follow best practices of database design, Embarcadero
hoffer to view the accompanying
video for this chapter.
C H A P T E R 2
Modeling Data in the