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CONCEPTUAL SCHEMA DESIGN PROCESS

Information Processing and Technology, 2001

Yr 12IPT

Last LessonThe UoD is the domain of relevant information. An information system is designed through the

Conceptual Schema Design Process (CSDP).The first process of the CSDP is to state elementary

facts. EF are simple, unambiguous, irreducible and do not

contain and, if, or, not, all, some, most.EF contain entities, roles, reference modes and values. The number of entities in an EF describes its arity.

.

Student (first name) Mary

studies / is studied by

Subject (name) IPT

Reference Scheme

Values = Mary, IPT

Entities = Student, Subject

Ref Modes = first name, name

Role = studies / is studied by

ArityThe arity of an elementary sentence is the

number of entities that associate or play roles

Mary Jogs - unary

Mary studies English - binary

Mary received a B for English - ternary

Design Cycle

1. State Elementary Facts

2.

3.

4.

6.

5.

Draw Conceptual Schema Diagram

Step 2. Draw Conceptual Schema Diagram

The Conceptual Schema Diagrams are a graphical representation of the elementary facts obtained from the first step.

•Entity types are represented by ellipses:

•Roles are represented by rectangles:

Data and EF’s ...Name Phone Suburb

Gary 4636 7345 Glenvale

Jenny 4636 2567 Mt Lofty

James 4636 6758 Mt Lofty

April 4636 4765 Middle Ridge

1. Person (name) Gary

has / refers to

Phone (Phone) 4636 7357.

2. Person (name) Gary

lives in / is lived in by

Suburb (suburb) Glenvale.

Elementary Facts:

… and a CS Diagram

Person (name)

Phone(Phone)

Suburb(suburb)

lives in

has

1. Person (name) Gary

has / refers to

Phone (Phone) 4636 7357.

2. Person (name) Gary

lives in / is lived in by

Suburb (suburb) Glenvale.

Ternary Relationship

Student Subject GradeMegan IPT HAMegan Physics SAMark Physics HA

1. Student (Student) Megan

studies

Subject (Subject) IPT

gainedResult (Grade) HA

Ternary Relationships

A ternary relationship is needed when two binary relationships do not convey the information required

Ternary relationships are drawn by nesting.

A Ternary Relationship

Student (student)

Result(grade)

Subject(subject)

studies

gained1. Student (student) Megan

studies

Subject (subject) IPT

gained

Result (grade) HA

Ternary or Binary?

Computer (Mhz) Hard Drive (Gb) Price ($)133 1.2 1997150 1.2 2153166 1.2 1357

133 1.7 2049150 1.7 2205

SummaryDrawing the CS Diagrams is the second step

of the CS Design Process.CS Diagrams are a graphical representation

of elementary facts.Ternary relationships require nesting.

Entity

(ref mode)

Entity

(ref mode)

plays role