systems analysis & design tenth...

Systems Analysis & Design

Tenth Edition

Chapter 11

Systems Implementation

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Phase Description

● Systems Implementation is the fourth of

five phases in the systems development

life cycle (SDLC)

● Includes application development,

testing, documentation, training, data

conversion, system changeover, and

post-implementation evaluation of the

results

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Introduction

● The system design specification serves as a

blueprint for constructing the new system

● The first task is application development

● Before a changeover can occur, the system

must be tested and documented carefully,

users must be trained, and existing data must

be converted

● A formal evaluation of the results takes place

as part of a final report to management

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Overview of Application Development

● Application development

● Objective is to translate the logical

design into program and code modules

that will function properly

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• Review the System Design• Requirements modeling • Functional decomposition diagrams (FDDs) • Structured data and process modeling• Data flow diagrams (DFDs) • Development strategy• Entity-relationship diagrams (ERDs)• User interface• Overall system architecture

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● Application Development Steps

– Start by reviewing documentation from prior SDLC phases and creating a set of program designs

– Planning(Ch.3-10)

– Module: related program code organized into small units that are easy to understand and maintain.

– After the design is created, coding can begin

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● System Development

Tools

– Entity-relationship

diagrams

– Flowcharts

– Pseudocode

– Decision tables and

decision trees

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• System Development Tools (Cont.)• DECISION TABLES AND DECISION TREES

• Used to model business logic for an information system

FIGURE 11-9 Sample decision tree that reflects the sales promotion

policy in Figure 11-8. Like a decision table, a decision tree shows the

action to be taken based on certain conditions

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● Project Management

– Even a modest-sized project might have

hundreds or even thousands of modules

– Important to set realistic schedules, meet project

deadlines, control costs, and maintain quality

– Should use project management tools and

techniques

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Structured Application Development

● Structure Charts

Structure charts: a tool to

show the program modules

and the relationships

among them

Module

A rectangle represents a

module

• Control module: a

higher-level module

• Subordinate modules:

lower-level modules

• Library module: reusable

code and can be invoked

from more than one

point in the chart

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– Data and controls are passed

between modules

– Data Couple: an empty-circle

arrow

– Control Couple: a filled-circle

arrow

• Flag（旗標）

• A module uses a flag to signal

a specific condition or action to

another module

– Fig. 11-11, p. 457

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An example of a structure chart with data and control couples

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– Condition: a line with diamond on one end

• A condition line indicates that a control module

determines which subordinate modules will be

invoked, depending on a specific condition

– Loop

• A loop indicates that one or more modules are

repeated

– Example: Figure 11-13, 11-14, pp. 457-458

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• Cohesion （內聚） and Coupling （結合）• Cohesion measures a module’s scope and

processing characteristics• A module that performs a single function or

task has a high degree of cohesion, which is desirable because it focuses on a single task and is much easier to code and reuse

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• Cohesion and Coupling （結合）• Coupling describes the degree of interdependence

among modules• Modules that are independent are loosely

coupled, which is desirable• Loosely coupled modules are easier to

maintain and modify, because the logic in one module does not affect other modules

• Tightly coupled modules have one module linked to internal logic contained in another module

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Cohesion and Coupling (Fig. 11-16)

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Structured Application Development● General guidelines for good module design: more

cohesive and loosely coupled

● Cohesion（內聚） and Coupling（結合）– Cohesion: a module that performs a single function or task has a

high degree of cohesion (good)

– If you need to make a module more cohesive, you can split it into

separate units, each of which performs a single function

– Example: p. 458, Figure 11-15

– Coupling: Modules that are independent are loosely coupled

(good)

– Loosely coupled: easy to maintain

– Tightly coupled: hard to maintain

– Status flag: an indicator that allows one module to send a

message to another module (poor design)

Example: p. 459, Figure 11-16

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● Drawing a Structure Chart

– Step 1: Review the DFDs

– Step 2: Identify Modules and Relationships

– Step 3: Add Couples, Loops, and Conditions

– Step 4: Analyze the Structure Chart and the

Data Dictionary

– Example p. 460, Fig. 11-17

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FIGURE 11-17 A structure chart

based on the order system DFDs

on pages 188, 192–193. The

three-level structure chart relates

to the three DFD levels

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Coding

● Programming Environments

– Each IT department has its own programming

environment and standards

– Integrated development environments (IDEs):

Microsoft .NET

• easier to program interactive software products by

providing built-in tools and advanced features, such

as real-time error detection, syntax hints, highlighted

code and version control

● Generating Code

– CASE can generate editable program code

directly from macros, keystrokes, or mouse

actions

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Testing the System

● After coding, a programmer must test

each program to make sure that it

functions correctly

● Syntax errors and Semantic errors

● Desk checking

– Looking for logic errors

● Structured walkthrough, or code review

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Testing the System

● Unit Testing

– The testing of an individual program or module

– Programmers must test programs that interact

with other programs and files individually

– Test data: correct and erroneous data

– Stub testing: simulation of each outcome by

displaying a message so that it is easier to link

with another program later

– Regardless of who creates the test plan, the

project manager or a designated analyst also

reviews the final test results

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Testing the System

● Integration Testing

– Integration testing, or link testing

– Testing the programs independently does not

guarantee that the data passed between them is

correct

– A testing sequence should not move to the

integration stage unless it has performed

properly in all unit tests

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Testing the System

● System Testing

– Aka Acceptance tests

– Major objectives:

• Perform a final test of all programs

• Verify that the system will handle all input

data properly, both valid and invalid

• Ensure that the IT staff has the

documentation and instructions needed to

operate the system properly and that backup

and restart capabilities of the system are

adequate

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Testing the System

● System Testing

– Major objectives:

• Demonstrate that users can interact with the

system successfully

• Verify that all system components are integrated

properly and that actual processing situations will

be handled correctly

• Confirm that the information system can handle

predicted volumes of data in a timely and efficient

manner

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Documentation

● Program Documentation

● System Documentation: data dictionary,

DFD,…

● Operations Documentation: scheduling

info for printed output, etc.

● User Documentation

– Online documentation, eg. FAQ’s

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Management Approval

● After system testing is complete, you

present the results to management

● If system testing produced no technical,

economical, or operational problems,

management determines a schedule for

system installation and evaluation

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System Installation and Evaluation

● Remaining steps in systems implementation:– Prepare a separate operational and test

environment

– Provide training for users, managers, and IT staff

– Perform data conversion and system changeover

– Carry out post-implementation evaluation of the system

– Present a final report to management

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Operational and Test Environments

● The environment for the actual systemoperation is called the operational environmentor production environment

● The environment that analysts and programmers use to develop and maintain programs is called the test environment

● A separate test environment is necessary to maintain system security and integrity and protect the operational environment

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Operational and Test Environments

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Training

● Training Plan

– The first step is to identify who should receive

training and what training is needed

– The three main groups for training are users,

managers, and IT staff

– You must determine how the company will

provide training

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Training

● Vendor Training– If the system includes the purchase of software or

hardware, then vendor-supplied training is one of the features you should include in the RFPs (requests for proposal) and RFQs (requests for quotation) that you send to potential vendors

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Training

● In-House Training– The IT staff and user departments often share

responsibility

– When developing a training program, you should keep the following guidelines in mind:• Train people in groups, with separate training

programs for distinct groups

• Select the most effective place to conduct the training

• Provide for learning by hearing, seeing, and doing

• Prepare effective training materials, including interactive tutorials

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Training

● In-House Training

– When developing a training program, you should

keep the following guidelines in mind:

• Rely on previous trainees

• Train-the-trainer strategy

– When Training is complete, many organizations

conduct a full-scale test, or simulation

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Data Conversion

● Data Conversion Strategies

– The old system might be capable of exporting

data in an acceptable format for the new

system or in a standard format such as ASCII or

ODBC

– If a standard format is not available, you must

develop a program to extract the data and

convert it

– Often requires additional data items, which

might require manual entry

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Data Conversion

● Data Conversion Security and Controls

– You must ensure that all system control

measures are in place and operational to protect

data from unauthorized access and to help

prevent erroneous input

– Some errors will occur

– It is essential that the new system be loaded

with accurate, error-free data

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System Changeover

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System Changeover

● Direct Cutover

– Involves more risk than other changeover

methods

– Companies often choose the direct cutover

method for implementing commercial software

packages

– Cyclical(週期性) information systems usually

are converted using the direct cutover method

at the beginning of a quarter, calendar year, or

fiscal year

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System Changeover

● Parallel Operation– Easier to verify that the new system is working

properly under parallel operation than under direct cutover

– Running both systems might place a burdenon the operating environment and cause processing delay

– Is not practical if the old and new systems are incompatible technically

– Also is inappropriate when the two systems perform different functions

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System Changeover

● Pilot Operation– The group that uses the new system first is

called the pilot site

– The old system continues to operate for the entire organization

– After the system proves successful at the pilot site, it is implemented in the rest of the organization, usually using the direct cutover method

– Is a combination of parallel operation and direct cutover methods

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System Changeover

● Phased Operation

– You give a part of the system to all users

– The risk of errors or failures is limited to the

implemented module only

– Is less expensive than full parallel operation

– Is not possible, however, if the system cannot

be separated easily into logical modules or

segments

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FIGURE 11-38 Relative risk and cost characteristics of the four changeover methods

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Post-Implementation Tasks

● Post-Implementation Evaluation– Includes feedback for the following areas:

• Accuracy, completeness, and timeliness of information system output

• User satisfaction

• System reliability and maintainability

• Adequacy of system controls and security measures

• Hardware efficiency and platform performance

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● Post-Implementation Evaluation

– Includes feedback for the following areas:

• Effectiveness of database implementation

• Performance of the IT team

• Completeness and quality of documentation

• Quality and effectiveness of training

• Accuracy of cost-benefit estimates and development

schedules

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– When evaluating a system, you should:

• Interview members of management and key users

• Observe users and computer operations personnel

actually working with the new information system

• Read all documentation and training materials

• Examine all source documents, output reports, and

screen displays

• Use questionnaires to gather information and opinions

from a large number of users

• Analyze maintenance and help desk logs

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– Users can forget details of the developmental

effort if too much time elapses

– Pressure to finish the project sooner usually

results in an earlier evaluation in order to

allow the IT department to move on to other

tasks

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Post-Implementation Tasks #

● Final Report to Management

– Your report should include the following:

• Final versions of all system documentation

• Planned modifications and enhancements to the

system that have been identified

• Recap of all systems development costs and

schedules

• A comparison of actual costs and schedules to the

original estimates

• Post-implementation evaluation, if it has been

performed

– Marks the end of systems development work

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