Chapter 6 -- Transition to System Design

8/2/2019 Chapter 6 -- Transition to System Design

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Phase 2Systems Analysis

Transition to Systems

DesignChapter 6


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Objective

Evaluate software alternatives anddevelopment strategies.

Explain advantages and disadvantages ofdeveloping in-house software versuspurchasing and customizing software.

Describe how companies use outsourcingand user applications.

List the steps in purchasing and evaluating asoftware package

Explain the differences between a request forproposal (RFP) and a request for quotation

(RFQ).


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Objective Describe the system requirements document

and the presentation to management at theend of the systems analysis phase.

Explain the transition from systems analysis

to systems design, and the differencebetween logical and physical design.

Explain the importance of prototyping anddescribe various prototyping methods, tools,and techniques.

Discuss the system design process.

Create and use appropriate codes during

systems design and development.


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SOFTWARE ALTERNATIVES

DEVELOP IN-HOUSE

PURCHASE SOFTWAREPACKAGES


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IN HOUSE

Software developed by technical

staff in a companys informationsystems department


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SOFTWARE PACKAGE

Software written by another

company and available forpurchase

commercial application software

available for sale by softwarepublishers or software vendors


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HORIZONTAL SOFTWARE

Software package that can beused by many different types oforganizationsAccounting

InvoicingAccounts payable


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VERTICAL SOFTWARE

Software developed to handlerequirements of IS for specific typeof organization

colleges

banks insurance companies

doctor offices


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Developing Your Own Software

Satisfy unique requirements

Minimize changes to businessprocedures and policies

meet constraints of existing system

meet constraints of existingtechnology

utilize new technology


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Buying a Software Package

Less expensive

Less time to implement

Fewer errorsAlready in use in other companies

Requires fewer technical staff for

developmentUpgraded by vendor

????????


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Customize Software Packages

Off the shelf package

vendors standard package

Customized package

a software package that YOU or

the VENDOR modify to meetyour unique specifications


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Customizing Software Packages

Vendor makes modifications

$$$$$ and time

YOU make modifications

time , money and technical

expertiseAdd on supplemental components


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Application Service Providers

ASP

Delivers applications, or access to

applications, by charging a usage orsubscription fee

Application hosting


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Outsourcing

Use of outside company to handle a portionof companys IT work load

Either temporary or long-term Advantages??

Disadvantages??

consulting firms

consultants

contract programmers


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User Applications

Typically use standard businesssoftware (Office 2000), to allow user to

perform tasks


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User Applications

Development of entire/portion of ISby end users for a company

limited to end user department

not integral to central IS

spreadsheets, database reportsoften 4th generation tools


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User Applications

WHY

NOT ENOUGH TIME FOR ISTO DO EVERYTHING


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Selecting Software Steps

1. Evaluate IS requirements

2. Identify potential software

vendors3. Evaluate software package

alternatives

4. Make the purchase

5. Install the software package


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Evaluate IS Requirements

Identify key features of IS

Identify IS current volume and futuregrowth

Specify IS external constraints

hardware and softwareREQUEST FOR PROPOSAL -- RFP


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Identify Potential Vendor

PC, midrange, mainframe,network????

Horizontal vs VerticalComputer store (PC only)

Hardware manufacturers

Industry trade magazines

Relative cost for pc vs mainframe


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EVALUATE SOFTWARE

PACKAGE ALTERNATIVES

Compare identified possible softwarepackage solutions

vendor presentations Existing users

benchmarks

literature evaluations in trade journals

evaluations from market research

try it yourself


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EVALUATE SOFTWARE

ALTERNATIVESBENCHMARK TEST

measure time it takes toprocess set number oftransactions

compare different softwareresults


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MAKE THE PURCHASE

WHAT DO YOU ACTUALLYPURCHASE??

SOFTWARE LICENSEright to use the software under

certain terms and conditions

single computer restriction verycommon


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MAKE THE PURCHASE

network?? -- site license

leasing agreementsMAINTENCE AGREEMENT

give you the right to contactvendor for assistance


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INSTALL SOFTWARE

IMPLEMENTATION

Load softwareTest software

Train end users

Convert data to system files


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HARDWARE

ALTERNATIVESRequest for Quotation

Request for Bid


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TURNKEY SYSTEM

Complete IS that includes allhardware, systems and application

software, documentation, training,installation, and support fromoutside vendor

Usually used in smaller companies


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COMPLETION OF SYSTEMS

ANALYSISSystems Requirement

Document

Formal Presentation


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SYSTEMS REQUIREMENTS

DOCUMENT Management Summary

IS Background

Functional Requirements Environmental Requirements

Alternatives

Recommended Alternatives Time and Cost Estimates

Appendices


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SYSTEMS REQUIREMENTS

DOCUMENTCould be lengthy!!!


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Presentations after Systems

Analysis PhaseOne of the most critical

milestones in entire SDLC


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POSSIBLE MANAGEMENT

DECISIONSDevelop in-house

Modify current system

Purchase software package

Purchase and develop in house

Perform additional systemsanalysis

Stop all further work


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CHANGE CONTROL

Process of managing andcontrolling the requestedchanges in requirements for aninformation system


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CHANGE CONTROL

Freeze the requirements

maximize chance forsuccessful delivery of IS thatsatisfies requirements within

projected costs and schedulesChange is inevitable


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Transition to Systems Design

Analysis Phase logical or essentialmodel

Logical design of IS defines the functionsand features of system and relationshipsamong its components

Includes the output that must be produced,

the input needed, processes that must beperformed

without regard to how tasks will be

accomplished physically


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Transition to Systems Design

Design Phase physical model Physical design of IS is a plan for the actual

implementation of the system

Built on logical design

Describes the actual processes ofentering, verifying and storing data,physical layout of data files, sortingprocedures, exact format ofreports


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PROTOTYPING

Early, rapidly developedworking version of IS thatexhibits the essential featuresof the target IS

working model


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Approaches to Prototyping

System prototyping full-featured,working model of IS, ready for

implementation RAD

Design prototyping (throwaway)

Used to verify user requirements, afterwhich the prototype is discarded

Gives us a user approved design


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PROTOTYPING TOOLS

Procedural vs. non-proceduraltools


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Prototyping Tools

Data Dictionary

RDBMS

report generator query language

screen generator

application generator

4 GL


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Prototyping during Systems

Analysisgiven to end users to evaluate how

well it satisfies their needs

working model -- changes made often

takes time to develop and evaluate

lower costs in later phases of SDLC


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CASE TOOLS

SOFTWARE PRODUCT THATAUTOMATES A SPECIFIC

SYSTEMS LIFE CYCLE TASKScreen generator

Computerized data dictionary

Advantages andDisadvantages ofCASE tools


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ALTERNATIVE GRAPHICAL

TOOLS

System flowchart


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SYSTEMS DESIGN

Look carefully at systemrequirements from systemsanalysis phase to completesystem design


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Components of IS areinterdependent

First must thoroughlyunderstand entire logical design

before beginning physicaldesign


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First step of System Design

Review system requirementsdocument from Systems Analysisphase

analyst assigned to design maynot have participated in analysis

time has passed since analysisphase


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SYSTEM DESIGN

ACTIVITIES

Need to consider IScomponents of data, datastores, people, procedures,hardware, software, and

informationinterrelationships


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DESIGN TIPS FOR

SYSTEM DESIGN

End user considerations

Data considerationsProcessing considerations


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Designing and using Codes

Code a set of letters or numbers thatrepresent a data item

Can be used to simplify output, inputand data formats

Consider early in design phase

Efficiency


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Types of Codes

Sequence

Block sequence

Alphabetic Category

Abbreviation

Significant digit


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Types of Codes

Derivation

Cipher

Action

Self-checking

Documents

Chapter 6 -- Transition to System Design