IS 421 Information Systems Analysis James Nowotarski 7 October 2002.

IS 421Information Systems Analysis

James Nowotarski

7 October 2002

• Understand basics of data modeling:– Defining entities

– Defining attributes

– Defining relationships

– Drawing entity-relationship diagrams (ERDs)

Today’s Objectives

Course Map

Contents

1. Introduction

Planning Phase2. Project Initiation3. Project Management

Analysis Phase4. Systems Analysis5. Gathering Information6. Process Modeling7. Data Modeling

1 2 3 4 6 7 8 9 10 115

Assignments

QuizzesFinal

Week

CoreExamReview

Topic Duration

• Recap Last Week 20 minutes

• Recap Assignments 1-2 10 minutes

• Quiz 45 minutes

*** Break 15 minutes

• Data Modeling: Lecture/Discussion 45 minutes

• Data Modeling: Group Exercises 45 minutes

• Assignment 3 Intro 10 minutes

Today’s agenda

Topic Duration



• Quiz 45 minutes


• Data Modeling: Lecture/Discussion45 minutes

*** Bears vs. Packers begins



Today’s agenda

Topic Duration



• Quiz 45 minutes





Today’s agenda

SDLC

The systems development life cycle (SDLC) is a description of the phases of an information system

Planning Analysis Design Implementation

Key Definitions

• The As-Is system is the current system and may or may not be computerized

• The To-Be system is the new system that is based on updated requirements

Analysis Phase

Analysis Phase

FromPlanningPhase:

System requestFeasibility analysisWorkplan . . .

DevAnalysisPlan

Examine-As-is

IdentifyImprove-ments

DevelopBasicSystemConcepts

DevelopDataModel

DevelopProcessModel

PrepareProposal

ToDesignPhase:

Deliverables:

Analysis Plan Functional Requirements

Quality Requirements

SystemConcept

Data Model

Process Model

System Proposal

Develop Conceptfor To-Be System

Analysis Phase

FromPlanningPhase:


DevAnalysisPlan

Examine-As-is



DevelopDataModel

DevelopProcessModel

PrepareProposal

ToDesignPhase:


Gather Analyze Specify

Three Fundamental Analysis Strategies

• Business process Automation (BPA)• Business Process Improvement (BPI)• Business Process Reengineering (BPR)

High-Level Work Plan for Analysis

Step Deliverable Technique

Planning PhaseAnalysis Phase

Examine As-Is System Information SummariesUse CasesProcess ModelData Model

Gather Information

Develop Process ModelDevelop Data Model

Identify Improvements Ideas for System Problem AnalysisRoot Cause AnalysisDuration AnalysisActivity-based CostingInformal BenchmarkingFormal BenchmarkingOutcome AnalysisBreaking AssumptionsTechnology AnalysisActivity EliminationProxy BenchmarkingProcess Simplification

Develop Concept for To-Be System

System ConceptUse CasesProcess ModelData Model

Gather Information

Develop Process ModelDevelop Data Model

Begin with the End in Mind

• Table of contents• Executive summary• System request• Work plan• Analysis strategy• Recommended

system• Feasibility analysis

• Process model• Data model• Appendices

System Proposal Outline

Information Gathering Techniques

• Interviewing• Joint application design• Questionnaires• Document Analysis• Observation

Interviews -- Five Basic Steps

• Selecting Interviewees• Designing Interview Questions• Preparing for the Interview• Conducting the Interview• Post-Interview Follow-up

Types of Questions

Types of Questions Examples

Closed-Ended Questions * How many telephone orders are received per day?

* How do customers place orders?* What additional information would you like the new system to provide?

Open-Ended Questions * What do you think about the current system?* What are some of the problems you face on a daily basis?* How do you decide what types of marketing campaign to run?

Probing Questions * Why?* Can you give me an example?* Can you explain that in a bit more detail?

Interview Report

INTERVIEW REPORT

Interview notes approved by: ____________

Person interviewed ______________Interviewer _______________Date _______________Primary Purpose:

Summary of Interview:

Open Items:

Detailed Notes:

JAD Key Ideas

• Allows project managers, users, and developers to work together

• May reduce scope creep by 50%• Avoids requirements being too specific or too

vague

Joint Application Design (JAD) Important Roles

• Facilitator• Scribe

JAD Meeting Room

JPEG Figure 5-5 Goes Here

Questionnaire Steps

• Selecting participants

– Using samples of the population• Designing the questionnaire

– Careful question selection• Administering the questionnaire

– Working to get good response rate• Questionnaire follow-up

– Send results to participants

Document Analysis

• Provides clues about existing “as-is” system• Typical documents

– Forms

– Reports

– Policy manuals• Look for user additions to forms• Look for unused form elements

Observation

• Users/managers often don’t remember everything they do• Checks validity of information gathered other ways• Behaviors change when people are watched• Careful not to ignore periodic activities

– Weekly … Monthly … Annual

Selecting the Appropriate Techniques

Interviews JAD Questionnaires Document Observation Analysis

Type of As-Is As-Is As-Is As-Is As-IsInformation Improve. Improve. Improve. To-Be To-Be

Depth of High High Medium Low LowInformation

Breadth of Low Medium High High LowInformation

Integration Low High Low Low Lowof Info.

User Medium High Low Low LowInvolvement

Cost Medium Low- Low Low Low- Medium Medium

Summary

• There are five major information gathering techniques that all systems analysts must be able to use: Interviews, JAD, Questionnaires, Document Analysis, and Observation.

• Systems analysts must also know how and when to use each as well as how to combine methods.

Topic Duration



• Quiz 45 minutes





Today’s agenda

Data Modeling in the Analysis Phase

FromPlanningPhase:


DevAnalysisPlan

Examine-As-is



DevelopDataModel

DevelopProcessModel

PrepareProposal

ToDesignPhase:

Deliverables:

Analysis Plan Functional Requirements

Quality Requirements

SystemConcept

Data Model

Process Model

System Proposal


Key Definitions

• A data model is a– Formal representation of the data to be used

for a business system.

• A data model should illustrate:– The people, places and things about which

data is collected,

– And how they are related to each other

Key Definitions

• A logical data model shows the logical organization of data– Without regard for how data gets stored,

created or manipulated• A physical data model shows how the data

will physically be stored in the database (secondary memory).– E.g. Oracle may store a customer table in

several files (cust1.dbf, cust2.dbf…) that span several hard drives.

Key Definitions

• Logical data model (Wixom and Dennis)• Data model• Conceptual data model• Entity model• Entity-relationship model• Entity-attribute-relationship model• Information model• Semantic data model

The collective output from logical data modeling is called various names

Data Modeling

• Entity-relationship diagram (ERD)• Entity descriptions• Attribute descriptions• Relationship descriptions• Domain descriptions (not covered here)

A logical data model deliverable includes an ERD and descriptions of entities, attributes, and relationships

Components of a Logical Data Model

An ERD Example

• Entities generally represent people, places, and things of interest to the organization (about which we would like to collect data).

• Represented as rectangle on the ERD

• Named with a singular noun (e.g., Patient)

What Is an Entity?

Entities and Instances

Instances are occurrences of an entity

What is an Attribute?

• An attribute is a characteristic or property of an entity.

• Attributes contain information that describes an entity.

• Attribute names are nouns (e.g, “name”).• Sometimes entity name is added at the

beginning of the attribute name (e.g., “vendor_name”).

Examples of Attributes

• Entity: Person– Attributes:

• first_name• last_name• eye_color• date_of_birth• address

• Entity: Classroom– Attributes:

• room_no• max_capacity

An ERD Example

Identifiers

• An identifier uniquely identifies each instance of the entity. It may consist of one or more attributes.

• Identifiers are also known generically as keys– Candidate keys = all identifiers for an entity

– Primary key = candidate key designated as “official” identifier

Examples of Identifiers

• What attribute uniquely identifies every instance of these entities?– Student

– Classroom

– Vehicle

Depicting Entities, Attributes and Identifiers

Entity name

Attributes

Identifier

Or, usecd_id (PK)

An ERD Example

Relationships

• Relationships represent connections, links, or associations between entities

• e.g., Patient-Appointment

• Relationships have some important properties:

1. Names, that should be active verbs– (A patient schedules appointments)

2. Cardinality

3. Modality.

Cardinality

• Cardinality refers to the number of times instances in one entity can be related to instances in another entity– One instance in an entity refers to one and only one

instance in the related entity (1:1)

– One instance in an entity refers to one or more instances in the related entity (1:M)

– One or more instances in an entity refer to one or more instances in the related entity (M:M)

Modality

• Modality refers to the minimum number of times that an instance in one entity can be related to an instance in another entity– One means that an instance in the related entity must

exist for an instance in another entity to be valid

– Zero means that no instance in the related entity is necessary for an instance in another entity to be valid

Some Ways to Depict Relationships

Patient Appointment

Patient Appointment

Patient Appointment

Patient Appointment

1 M

schedules

schedules

Is scheduled by

Same

e.g., A patient may have zero to

many appointments

Meanings of the Crow’s Feet

Min MaxCardinality

0 1

1 1

0 M[any]

1 M[any]

The Entity-Relationship Diagram (ERD)

An ERD Example

What Is an ERD?

• A picture of the logical data model, – i.e., an ERD shows the information created,

stored, and used by a business system.

An ERD ExampleA patient must have at least 1 appointment

Topic Duration



• Quiz 45 minutes





Today’s agenda

Exercise• SkyHigh Airlines has three major resources: airplanes, pilots, and crew members. Pilots and crew members have home bases, which they return at the end of an assigned flight. A flight must have exactly one pilot and one or more additional crew members along with an airplane. Each

airplane has a maintenance base.

• Draw an ERD showing:• Entities• Relationships

• Cardinality• Modality

• 10 minutes

Group Exercise

• Textbook, p.209, Exercise D-1• Show:

• Entities• Attributes• Identifier(s)• Relationships

• Cardinality• Modality

• 15 minutes

Still More Definitions

• A foreign key is all of these things:• a primary key of one entity (sometimes called parent

entity),

• duplicated in another entity (child entity)

• provides a common linkage between the two entities

Foreign Key Example

• Customer(cust_id (PK), cust_name)• Order (ord_no (PK), cust_id (FK), ord_date)

Customers(Parent)

cust_id cust_name

100 Slick Willy, Inc.

200 George_W, Co.

300 Gore, Ltd.…

ord no cust_id ord_date

2100 200 13-Sep-2000

2101 100 14-Nov-20002102 100 23-Dec-20002103 100 24-Dec-2000…

Orders(Child)

A foreign key is a primary key of one entity that is duplicated in another entity to provide a common linkage between entities. Why use them?

PKFKCust_id

Entity Types1. Independent2. Dependent3. Intersection

Independent Entities

• An independent entity exists without the help of another entity– Common entities such as student, professors,

customers, products

– The identifier is created by the entity’s own attributes

– Usually on the “1” side of a relationship

– a.k.a. fundamental entity (in Visual Analyst, e.g.) or strong entity

Dependent Entities

• Alternatively, a dependent entity cannot exist without the help of another entity– Special entities such as emp_dependent

(needs an employee to exist)

– The identifier is usually based on another entity’s attributes (emp_ssn & dep_ssn)

– Usually on the “M” side of a relationship

– a.k.a. attributive entity (in Visual Analyst, e.g.) or weak entity

Intersection entities

• An intersection entity exists based on the relationship between two entities.– They have attributes that are peculiar to the

relationship between those entity instances, not the individual entities themselves

– They are created to store information about two entities sharing an M:M relationship

– a.k.a. associative entities, gerunds

Intersection Entity Example

A student may take many classes.A class may have many students.Where are grades stored?

Student Class

An instance in the student entity is related to _____instances in the class entity.

An instance in the class entity is related to _____instances in the student entity.

RosterStudent Class

An ERD Example: CD’s Relationships Expanded

An Intersection Entity Example

A CD may be a part of many orders.

An order may contain many CDs.

The CD-order relationship is M:M.

Where do you store quantity of CD’s on an

order?

Adding Intersection Entities

1. Create an intersection entity

(line item).

3. The “1” side goes

on the original

entities.

2. Move the “M’s” are adjacent to

the intersection entity.

M:N to 1:Ms

• Rule: The M always go to the intersection entity. Why?

Orders

CD_No CD_Title Order_No CD_No Qty Order_No234 Best of Lawrence Welk 100101 234 12 100101235 Living Daylights Soundtrack 100101 236 3 100102236 Moody Blues Greatest Hits 100102 234 5 100108

100102 235 2100102 236 6100108 236 1

CD Line Items

Creating An Entity-Relationship Diagram

Steps in Building Data Models1. Review existing data models2. Define entities

a. Independentb. Dependent, including Intersection entities

3. Define attributes and keys (primary, foreign)4. Define relationships5. Finalize ERD6. Normalize7. Integrate data models as required8. Verify completeness of the data model9. Validate the data model

a. With usersb. With the enterprise’s data administrator

Design Guidelines

• Best practices rather than rigid rules• Entities should have many instances (don’t include

fixed items such as stationery headings)• Avoid unnecessary attributes (outside the scope of

your system)• Apply correct cardinality and modality• Labels reflect common business terms• Assumptions should be clearly stated

Summary

• The ERD is the most common technique for drawing data models. The building blocks of the ERD are:– Entities (nouns), describe people, places, or

things– Attributes (nouns), capture information about

the entity– Relationships (active verb sentences)

associate data across entities; they have cardinality and modality

End of Slides - Extra slides follow

Metaphors

ER Model Relational Model

Database Spreadsheet

Entity Relation Table, File Table

Instance Tuple Record Row

Attribute Attribute Field Column

Identifier Key Key Key

Identifiers

• An identifier should have the following characteristics:– Its value should not change over the life of

each instance

– Its value should never be “null” or empty

– It should be composed of the minimal number (preferably one) of attributes required to ensure uniqueness

Some Ways to Depict Relationships

Entity 1 Entity 2

Entity 1 Entity 2

Entity 1 Entity 2

1:1

1:M

1:0 or M

Data Modeling

To identify entity types, look for nouns in the requirements

Customers will access the Internet sales system to look for CDs of interest. Some customers will search for specific CDs or CDs by specific artists, whereas other customers want to browse for interesting CDs in certain categories (e.g., rock, jazz, classical). When the customer has found all the CDs he or she wants, the customer will check out by providing personal information regarding the order (e.g., the CDs to purchase and quantity for each item). The system will verify the customer’s credit card information with an on-line credit card clearance center and either accept the order or reject it.

- Dennis & Wixom, p.159

IS 421 Information Systems Analysis James Nowotarski 7 October 2002.

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