Systems analysis and development CIS210 ch 09

CIS 210
Systems Analysis
and Development
Week 6 Part I
Structuring Systems
Data Requirements


Objectives
• Upon completion of part I you will be able to:
– Understand and be able to explain the concepts related to data
modeling terms
– Understand and be able to draw entity relationship diagrams
– Understand and be able to explain the concepts related to
conceptual data modeling
– Understand and be able to explain the concepts related to
distinguish between unary, binary, and ternary relationships
– Understand and be able to explain the concepts related to
defining rules for business use in E-R diagrams


Overview
• Data Modeling: Why is it Important?
– Characteristics of data are crucial
– Data are most complex aspects of information
systems
– Data characteristics reasonably permanent

• E-R Diagramming / Class Diagramming
– Explain structure of data
– Mastery is crucial to success

Conceptual Data
Modeling
• What is a Conceptual Data Model
– Representation of organizational data
– Rules and meaning of data

• Conceptual Data Modeling Process
– Develop model for existing system
– Develop model for new system
– Encapsulates all SDLC phases

• Deliverables
– E-R diagram
– Entries in data dictionary


Gathering
Information
• Top-Down Approach
– Understanding of the nature of the business
– No specific information requirements

• Bottom-Up Approach
– Specific business documents
• Computer displays
• Reports
• Business forms

Introduction to
E-R Modeling
• Overview
– E-R model
– E-R Diagram

• Entities
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–
–
–

Entity type
Entity instance
Naming and defining types
Attributes
• Naming and defining attributes
• Multi-valued attributes

– Candidate keys and identifiers

• Relationships
– Associations


Conceptual Data
Modeling and the ER Model
• Degree of Relationship
– Unary

– Binary
– Ternary

• Cardinalities in Relationships
– Minimum
– Maximum

• Naming and Defining Relationships
– Naming guidelines
– Guidelines for defining

• Associative Entities


Representing
Supertypes & Subtypes
• Subtype
– Sub grouping of entities

• Supertype
– Generic entity type

• Relationship Rules
–
–
–
–

Total specialization
Partial specialization

Disjoint rule
Overlap rule


Business Rules
• Types of Business Rules
– Entity integrity
– Referential integrity constraints
– Domains
• Domain definitions

– Triggering operations
• Components
–
–
–
–
–

User rule
Event
Entity name
Condition
Action


Packaged Conceptual
Data Models
• Overview
– Comparatively low cost

– Generic data models
– Developed by specialists

• Types of Packaged Data Models
– Universal
– Industry specific

• Benefits
– Time
– Cost
– Quality


Object Modeling
•

Representing Objects and Classes
–
–
–
–
–
–

•

Types of operations
–
–
–

–

•

Object
State
Behavior
Object class
Class diagram
Operation
Constructor
Query
Update
Scope

Representing
–
–
–
–

Associations
Association Classes
Derived Attributes, Associations, and Roles
Generalization


Summary
•
•

•
•
•
•
•

Conceptual Data Modeling
Gathering Information
E-R Modeling
Supertypes and Subtypes
Business Rules
The Role of Packaged Conceptual Data Models
Object Modeling