1. LIS 384K.11 Database-Management Principles and Applications
Basic Concepts of
Entity-Relationship Analysis
R. E. Wyllys
Last revised 2002 Feb 18
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

2. What Is Entity-Relationship Analysis?
E-R analysis endeavors to
Identify major ingredients, entities, of a complicated situation
Identify characteristics, attributes, of the major ingredients
Uncover and analyze interconnections, relationships, among the major ingredients
Assess various aspects of the relationships
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

3. E-R Analysis In short, E-R analysis strives
to take a close look at the ingredients of a puzzle
in order to identify major and minor ingredients
and to figure out how they relate to each other
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

4. E-R Analysis
E-R analysis can be summarized as the process of uncovering, analyzing, and explicating (i.e., stating clearly and fully) the business rules governing a complicated situation
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

5. Business Rules Rob and Coronel1 say:
Business rules are precise statements, derived from a detailed description of the organization's operations, that define one or more of the following modeling components:
Entities
Relationships
Attributes
Connectivities
Cardinalities
Constraints
1Rob, P.; Coronel, C. Instructor’s Manual to Accompany Database Systems: Design, Implementation, and Management. Fourth Edition. CD-ROM
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

6. Business Rules Examples of business rules1
An invoice contains one or more invoice lines, but each invoice line is associated with a single invoice. That is,
An invoice contains one or more invoice lines.
Each invoice line is associated with a single invoice.
A store employs many employees, but each employee is employed by only one store.
A college has many departments, but each department belongs to a single college. (This business rule reflects a university that has multiple colleges such as Business, Liberal Arts, Education, Engineering, etc.)
1From: Rob, P.; Coronel, C. Instructor’s Manual to Accompany Database Systems: Design, Implementation, and Management. Fourth Edition. CD-ROM
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

7. Business Rules Examples of business rules1 (cont'd)
A driver may be assigned to drive many different vehicles, and each vehicle can be driven by many drivers. (Note: Keep in mind that this business rule reflects the assignment of drivers over a period of time.)
A client may sign many contracts, but each contract is signed by only one client.
A sales representative may write many contracts, but each contract is written by one sales representative
1From: Rob, P.; Coronel, C. Instructor’s Manual to Accompany Database Systems: Design, Implementation, and Management. Fourth Edition. CD-ROM
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

8. Business Rules Some business rules for a library
Books and other materials exist in various editions and numbers of copies
Books may or may not circulate
Books that circulate may do so for varying periods
Periods may be determined by
Book status alone
Borrower status alone
Combination of book status and borrower status
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

9. Business Rules More business rules for a library
Users may have various statuses
Users may have varying numbers of items currently charged out to them
Users may or may not owe fines
Fine status may or may not affect eligibility to borrow
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

10. Business Rules More business rules for a library
Staff members have attributes of
Salary or wage rates
Annual leave
Sick leave
Work schedules
Job titles
Special skills (e.g., languages, puppetry)
Hire dates
Total length of service
Professional organization memberships
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

11. Business Rules More business rules for a library
Physical facilities include
Branches
Furniture
Machines (e.g., computers, microform readers, automobiles, players for CD-ROMs, audiotapes, videotapes)
Library-management software
Catalog records (e.g., computerized databases, catalog cards)
Records of inventory, acquisitions, circulation, personnel
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

12. Business Rules More business rules for a library
Related organizations may include
City, university, or corporate administrations
Employee unions
Friends of the Library organizations
Vendors of books, serials, and other products and services used by the library
Networks of which the library is a member (e.g., OCLC, Amigos, Association of Research Libraries, Texas State Library network, Central Texas Library System)
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

13. E-R Diagrams E-R analysis relies heavily on diagrams to represent
Entities (rectangles)
Attributes (ellipses)
Relationships (diamonds)
Connections (lines, which may have arrowheads or crowsfeet to represent degrees of connectivity or relationship)
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

14. Crucial Use of E-R Analysis
It is especially important to identify and note many-to-many (M:N) relationships: for example1
Note: The small circle denotes optionality (a person need not be a customer; but to be a customer, he or she must rent at least one tape)
1From: Rob, P.; Coronel, C. Instructor’s Manual to Accompany Database Systems:
Design, Implementation, and Management. Fourth Edition. CD-ROM
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

15. Crucial Use of E-R Analysis
The typical resolution of many-to-many (M:N) relationships is by a bridge table (also called a composite entity)
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

16. Crucial Use of E-R Analysis
A further explication of the resolution of the M:N relationship
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications

17. E-R Analysis Is Part Science, Part Art
GSLIS - The University of Texas at Austin
LIS 384K.11, Database-Management Principles and Applications