Advanced Accounting Information Systems

1
Enterprise Information Systems A Pattern-Based
ApproachBy Dunn, Cherrington, and Hollander
Chapter 4, Part 1 The REA Enterprise
OntologyBusiness Process Level Modeling Edited
by J Welch
Acknowledgement Many of the slides in this
chapter are based on class materials prepared by
William E. McCarthy at Michigan State University
and are used with his permission
2
Conceptual Modeling Constructs

• Entities
• Sets of real world objects things that have a
  separate existence, either physical or conceptual
• Note SETS
• Relationships
• Sets of associations between entities
• Again, note SETS
• Degrees of relationships

3
Conceptual Modeling Constructs

• Attributes
• Characteristics or elementary properties of
  entities and/or relationships
• Primary key attribute uniquely and universally
  identifies each instance of an entity or
  relationship set
• Simple versus composite attributes
• Derivable attributes

4
Conceptual Modeling Constructs

• Participation Cardinalities (Min,Max)
• Minimum cardinality expresses the minimum
  number of times one instance of an entity set
  must participate in a relationship. 0
  optional participation 1 mandatory
  participation
• Maximum cardinality expresses the maximum
  number of times one instance of an entity set may
  participate in a relationship 1 one-time only
  participation N as many times as needed, no
  restrictions

5
Entity-Relationship (ER) Diagram Notation

• Most conceptual models are created with some
  version of the ER Diagram
• Several variations exist, and notation
  (especially for cardinalities) differs between
  the variations

6
Representing Entities in Conceptual Modeling
Notation

• In ER Diagrams, entities are represented as
  rectangles (each rectangle is labeled with the
  entity name)

7
Examples Customer, Sale

• ER Diagram format

One rectangle for each resource, event or agent.
8
Representing Relationships in Conceptual Modeling
Notation

• In ER Diagrams, relationships are represented
  with diamonds attached by straight lines to the
  entities for which the relationship depicts an
  association.

9
Example Sale IS-MADE-TO Customer

• ER Diagram format

10
Representing Attributes in Conceptual Modeling
Notation

• In ER Diagram format, attributes are depicted
  with small circles attached by short lines to the
  applicable entities and/or relationships. The
  circles for primary key attributes are darkened.

11
Example Customer Characteristics

• In ER diagram format

12
Representing Participation Cardinalities in
Conceptual Modeling Notation

• In ER Diagram format, participation cardinalities
  are included as labels on the line between the
  entity and the relationship for which the
  participation cardinality applies.

13
Example Participation cardinalities

• Question1 Can you have an Employee with no
  department assigned?
• Employees are not necessarily assigned to
  departments
• Minimum participation of employee 0
• Question 2 Does an Employee have one department
  or more than one department?
• An employee can work for no more than one
  department
• Maximum participation of employee 1
• Question 3 Can you have a department without an
  employee?
• Every department has at least one employee
  assigned to it
• Minimum participation of department 1
• Question 4 Does a department may have one or
  many employees assigned to it?
• A department has multiple employees
• Maximum participation of department N

14
Example Participation Cardinalities

• In ER Diagram format

(0,1)
(1,N)

• Employees are not necessarily assigned to
  departments

• An employee can work for no more than one
  department

• Every department has at least one employee
  assigned to it

• A department may have many employees assigned to
  it

15
Examples Participation Cardinalities in Marriage
Relationship

• Example 1 At any given time, each man may have
  at most one wife and each woman may have at most
  one husband.
• In other words, our database is only capturing
  current marriages, and if one dissolves it will
  be completely removed from our database

(0,1)
(0,1)
16
Examples Participation Cardinalities in Marriage
Relationship

• Example 2 At any given time, a woman may be
  married to more than one man, but a man may be
  married to only one woman.
• In other words, a non-realistic example!

(0,N)
(0,1)
17
Examples Participation Cardinalities in Marriage
Relationship

• Example 3 At any given time, a man may be
  married to more than one woman, but a woman may
  be married to only one man.
• In other words, another non-realistic example!

(0,1)
(0,N)
18
Examples Maximum Participation Cardinalities in
Marriage Relationship

• Example 4 Any man may have many wives, and any
  woman may have many husbands.
• In other words, our database needs to include
  current and previous marriages.

(0,N)
(0,N)