Systems analysis and design methods 7th whitten and benley chapter 09

Systems Design and ConstructionStrategies For System Design  Strategies For System Design  There are also many strategies or techniques for performing systems design and they include:

Trang 1

Systems Design and Construction

Introduction

 The chapter will address the following questions:

 What is the systems design process in terms of the configuration, procurement, and design and integration phases of the life cycle

 What are the configuration, procurement, and design and

integration phases in terms of your information building blocks

 What are the configuration, procurement, and design and

integration phases in terms of purpose, activities, roles, inputs and outputs, techniques, and steps

 What the traditional and prototyping approaches to systems

design

Trang 2

What is System Design?

 Systems design is the evaluation of alternative solutions and the

specification of a detailed computer-based solution It is also

called physical design.

 Systems analysis primarily focused on the logical,

implementation-independent aspects of a system (the

requirements)

 Systems design deals with the physical or

implementation-dependent aspects of a system (the system's technical

specifications)

Trang 3

Configuration Phase

Procurement Phase

Design

&

Integration Phase

Repository

SYSTEMS DESIGN

Technology Requirements

Design Requirements

Technology Integration Requirements

to the construction phase

Documentation

Trang 4

Strategies For System Design

 Strategies For System Design

 There are also many strategies or techniques for performing

systems design and they include:

 Modern Structured Design

 Information Engineering (IE)

 Prototyping

 Object-Oriented Design (OOD)

 These strategies are often viewed as competing alternative

approaches to systems design, but in reality, certain combinations complement one another

Trang 5

 Structured design techniques help developers deal with the size and complexity of programs

 Modern Structured Design is a process-oriented technique for

breaking up a large program into a hierarchy of modules that result in a computer program that is easier to implement and maintain (change) Synonyms (although technically inaccurate) are top-down program design and structured programming

subprogram, or subroutine

Trang 6

 Structured design seeks to factor a program into the top-down hierarchy of modules that have the following properties:

 Modules should be highly cohesive; that is, each module

should accomplish one and only one function

 Modules should be loosely coupled; in other words, modules

should be minimally dependent on one another

have on other modules.

Trang 7

 Structured design is performed during systems design

 Structured design does not address all aspects of design – for instance, structured design will not help you design inputs, databases, or files

 The software model derived from structured design is called a

structure chart.

 The structure chart is derived by studying the flow of data through the program

Trang 8

1.2 Approve applicant

1.2.2 Determine acceptance

1.2.1 Get past member account

standing

1.2.3 Record reviewed application

1.2.3.1 Reject applicant

1.2.3.2 Accept applicant Past Member

Rejected application

New member details

Subscriber's name

Standing and time account closed

Acceptance decision

Reviewed application

Trang 9

 Information Engineering (IE)

 IE involves conducting a business area requirements analysis from which information system applications are ‘carved out’ and

prioritized

 Information Engineering is lacking on the design process

 The applications identified in IE become projects to which other

systems analysis and design methods are intended to be applied in

order to develop the production systems

Trang 10

 Prototyping

 A prototype, according to Webster's dictionary, is ``an original or model on which something is patterned'' and/or ``a first full-scale and usually functional form of a new type or design of a

construction (as an airplane).''

 Engineers build prototypes of engines, machines, automobiles, and the like, prior to building the actual products

 Prototyping allows engineers to isolate problems in both

requirements and designs

 The prototyping approach is an iterative process involving a close working relationship between the designer and the users

Trang 11

participation

development that is, end-users tend to change their minds

requirements until they see them implemented

see, touch, feel, and experience

specification, with one exception errors can be detected much earlier

Trang 12

 Prototyping

 The prototyping approach has several advantages (continued)

 Prototyping can increase creativity because it allows for quicker user feedback which can lead to better solutions

 Prototyping accelerates several phases of the life cycle, possibly bypassing the programmer

Trang 13

 Prototyping

repair'' life cycle that used to dominate information systems

phases

specification

quickly expand beyond original plans

Trang 14

 Prototyping

 The prototyping approach has several disadvantages (continued)

 Prototyping can reduce creativity in designs

 Prototypes often suffer from slower performance than their third-generation language counterparts

Trang 15

 The prototype is then corrected, enhanced, or refined to reflect the new requirements

 The revision and review process continues until the prototype

is accepted

Trang 16

 JAD is a technique that complements other systems analysis and

design techniques by emphasizing participative development

among system owners, users, designers, and builders

 During JAD sessions for systems design, the systems designer will take on the role of facilitator for possibly several full-day

workshops intended to address different design issues and

deliverables

Trang 17

 Rapid application development (RAD) is the merger of various

structured techniques (especially the data-driven information

engineering) with prototyping techniques and joint application development techniques to accelerate systems development

 RAD calls for the interactive use of structured techniques and prototyping to define the users’ requirements and design the final system

Trang 18

 Using structured techniques:

 The developer first builds preliminary data and process models

of the business requirements

 Prototypes then help the analyst and users to verify those requirements, and to formally refine the data and process models

 The cycle of models, then prototypes, then models, then prototypes, and so forth ultimately results in a combined business requirements and technical design statement to be used for constructing the new system

Trang 19

 Object-oriented design (OOD) techniques are used to refine the

object requirements definitions identified earlier during analysis, and to define design specific objects

 Based on a design implementation decision, during OOD the

designer may need to revise the data or process characteristics for

an object that was defined during systems analysis

 Likewise, a design implementation decision may necessitate that the designer define a new set of objects that will make up an

interface screen that the user(s) may interact with in the new

system

Trang 20

Fast System Analysis Methods

 The FAST methodology does not impose a single design technique

on system developers

discussed: structured design (via process modeling), information engineering (via data modeling), prototyping (via rapid application development), joint application development (for all methods), and rapid application development

 Progressive FAST developers can use object-oriented design in

conjunction with object technology for prototyping to fully exploit the object paradigm

Trang 21

The Configuration Phase of Systems Design

 Configuration Phase

 The purpose of the configuration phase is to identify candidate solutions, analyze those candidate solutions, and recommend a target system that will be designed and implemented

 The fundamental objectives of the configuration phase are:

 To identify and research alternative manual and based solutions to support our target information system

computer- To evaluate the feasibility of alternative solutions and recommend the best overall alternative solution

 The configuration phase marks the first point in the systems

development process that we have placed emphasis on how the new system might operate

Trang 22

INFORMATION SYSTEMS FRAMEWORK

SYSTEM DESIGNERS (specification)

SYSTEM USERS (requirements)

SYSTEM OWNERS (scope)

Database Technology

(and standards)

Data Requirements

Business Subjects

FOCUS ON SYSTEM DATA

Business Processes

Business Functions

FOCUS ON SYSTEM PROCESSES

Interface Requirements

System Context

FOCUS ON SYSTEM INTERFACES

Software (and Hardware) Technology

(and standards)

Interface Technology

(and standards)

Networking Telchnology

(and standards)

Communication Reqts.

Operating Locations

FOCUS ON SYSTEM GEOGRAPHY

Definition Phase Study Phase

REASON

Methodology

Customers order zero, one, or more products

Products may be ordered

by zero, one, or more customers.

Marketing Advertising Orders Sales Cancellations Services

Order Management Syst em Cust omer

Acco unt s Receivable Dat abase

Warehouse

Bank

Orde r Picking Order Credit

Credit Voucher

CUSTOMER customer-no customer-name customer-rating balance-due

PRODUCT product-no product-name unit-of-measure unit-price quantity-available ORDER order-no order-date products-ordered quantities-ordered

Check credit Validate customer Validate

Release order

Customers

Orders

Products order customer number valid order order without valid customer

credit order with valid products approved order

quantity approved order rejected order

prices picking ticket

Fire c ra ck e r Sal e s

EDI Cust

St Louis HQ

LA Office Indy Ware- NY Office

West Customers Customers East

Maintenance Records

Products Catalog

order cat alog ship order ship order ship order credit credit service

Survey Phase

Configuration

Trang 23

1 Define Candidate Solutions

2 Analyze Feasibility of Alternative Solutions

3 Recommend

Approval

to continue

Outside Sources

H/W & S/W Costs and References

H/W & S/W Specifications

Candidate Solutions

Business Reqmts Outline

&

Approved Tech

Architecture

Candidate Solutions Feasibility Analysis

System

Proposal Changes to

Proposed Design

Proj Plan, Size Estimates, Candidate Solutions,

& Feasibility Analysis

to the procurement phase

to the design and integration phase

Technology Requirements

Trang 24

 Activity: Define Candidate Solutions

 Given the business requirements established in the definition

phase of systems analysis, we must identify alternative candidate solutions

 Purpose

 The purpose of this activity is to identify alternative candidate solutions to the business requirements defined during systems analysis

Trang 25

 Roles

 The activity is facilitated by the project manager.

 System owner roles - system owners are not normally directly involved in this activity

 System user roles - users are typically not involved in this activity at this time

 System analyst roles - The systems analyst is most knowledgeable about the business requirements and therefore should be involved in brainstorming solutions that might fulfill those requirements

Trang 26

role in this activity and will usually seek the input and advice from the following expertises:

regarding available database technology

existing network technology

new and existing applications development tools and standards

in this activity

Trang 27

 Prerequisites (Inputs)

 This activity is triggered by the approval from the system owners to continue the project into systems design

 The key inputs are:

• business requirements outline defined during systems analysis

• hardware and software specifications from various sources such

as vendors and customer referrals

• approved technology architecture

Trang 28

 Deliverables (outputs)

 The principle deliverables of this activity are the candidate

solutions for a new system.

 A matrix is a useful tool for effectively capturing, organizing, and communicating the characteristics for candidate solutions

Trang 29

Characteristics Candidate 1 Candidate 2 Candidate 3 Candidate

Portion of System Computerized

Brief description of that portion of the system that would be computerized in this candidate.

COTS package Platinum Plus from Entertainment Software Solutions would be purchased and customized to satisfy Member Services required functionality.

Member Services and warehouse operations in relation to order fulfillment.

Same as candidate 2.

Benefits

Brief description of the business benefits that would be realized for this candidate.

This solution can be implemented quickly because its a purchased solution.

Fully supports user required business processes for Soundstage Inc Plus more efficient interaction with member accounts.

Servers and Workstations

A description of the servers and workstations needed to support this candidate.

Technically architecture dictates Pentium pro, MS Windows NT class servers and Pentium, MS Windows

NT 4.0 workstations (clients).

Same as candidate 1 Same as candidate 1.

Software Tools Needed

Software tools needed to design and build the candidate (e g., database management system, emulators, operating systems, languages, etc.) Not generally applicable if applications software packages are to be purchased.

MS Visual C++ and MS ACCESS for customization

of package to provide report writing and integration.

MS Visual Basic 5.0 System Architect 3.1 Internet Explorer

Application Software

A description of the software to be purchased, built, accessed, or some combination of these techniques.

Package Solution Custom Solution Same as candidate 2.

Method of Data Processing

Generally some combination of: on-line, batch, deferred batch, remote batch, and real-time.

Client/Server Same as candidate 1 Same as candidate 1.

Output Devices and Implications

A description of output devices that would be used, special output requirements, (e.g network, preprinted forms, etc.), and output considerations (e.g., timing constraints).

(2) HP4MV department Laser printers (2) HP5SI LAN laser printers

(2) HP4MV department Laser printers (2) HP5SI LAN laser printers (1) PRINTRONIX bar-code printer (includes software &

drivers) Web pages must be designed

to VGA resolution All internal screens will be designed for SVGA resolution.

Input Devices and Implications

A description of Input methods to be used, input devices (e.g., keyboard, mouse, etc.), special input requirements, (e.g new or revised forms from which data would be input), and input considerations (e.g., timing of actual inputs).

Keyboard & mouse Apple “Quick Take” digital

camera and software (15) PSC Quickscan laser bar-code scanners (1) - HP Scanjet 4C Flatbed Scanner

Keyboard & mouse

Storage Devices and Implications

Brief description of what data would be stored, what data would be accessed from existing stores, what storage media would be used, how much storage capacity would be needed, and how data would be organized.

MS SQL Server DBMS with 100GB arrayed capability. Same as candidate 1. Same as candidate 1.

Trang 30

 Applicable Techniques

 The following techniques are applicable to this activity

• Fact Finding Fact finding methods are used to interact with

outside sources such as hardware and software vendors and stores

to gather product specifications for each candidate

Trang 31

 Steps

 The following steps are suggested to complete this activity

• Step 1 - Review the business requirements outlined in the

definition phase of systems analysis.

• Step 2 - If it exists, review the technology architecture to

determine and hardware or software standards required for any candidate solution.

• Step 3 - Brainstorm alternative solutions that fulfill the business

requirements Also, identify solutions that were suggested prior to the design phase

• Step 4 - Research technical specifications detailing the

characteristics of each candidate solution.

Trang 32

 Activity: Analyze Feasibility of Alternative Solutions

 Feasibility analysis should not be limited to costs and benefits

 Most analysts evaluate solutions against four sets of criteria:

• Is the solution technically practical?

• Does our staff have the technical expertise to design and build this

solution?

• Will the solution fulfill the user's requirements?

Trang 33

without regard to the feasibility of other candidates.

 Purpose

solutions according to their economic, operational, technical, and schedule feasibility.

Trang 34

 Roles

 The activity is facilitated by the project manager

 System owner roles - The opinions of the following individuals may be sought when assessing the operational feasibility of a candidate solution:

manager

 System user roles - several users may be involved to assess their feelings toward a candidate solution

for determining the financial techniques to be used when analyzing

Trang 35

the technical feasibility of a of the technology for candidate solution:

Applications administer

 System builder roles are not typically involved in this activity unless deemed appropriate by a system owner

Trang 36

 Prerequisites (Inputs)

 This activity is triggered by the definition of one or more

candidate solutions

 To conduct the feasibility analysis, hardware and software

costs as well as feedback from customer references are

needed

 Deliverables (outputs)

 The principle deliverable of this activity is the completed

feasibility analysis for each candidate.

 A matrix can be used to communicate the large volume of information about candidate solutions

Trang 37

Operational Feasibility

Functionality A description of to what

degree the candidate would benefit the

organization and how well the system

would work.

Political A description of how well

received this solution would be from

both user management, user, and

organization perspective.

30% Only supports Member Services requirements and current business processes would have to be modified to take advantage of software functionality

Technology An assessment of the

maturity, availability (or ability to

acquire), and desirability of the

computer technology needed to support

this candidate.

Expertise An assessment to the

technical expertise needed to develop,

operate, and maintain the candidate

system.

30% Current production release of Platinum Plus package is version 1.0 and has only been

on the market for 6 weeks.

Maturity of product is a risk and company charges an additional monthly fee for technical support.

Required to hire or train C++

expertise to perform modifications for integration requirements.

Score: 50

Although current technical staff has only Powerbuilder experience, the senior analysts who saw the MS Visual Basic demonstration and presentation, has agreed the transition will be simple and finding experienced VB programmers will be easier than finding Powerbuilder programmers and at a much cheaper cost.

MS Visual Basic 5.0 is a mature technology based on version number.

Score: 95

Although current technical staff is comfortable with Powerbuilder, management is concerned with recent acquisition of Powerbuilder

by Sybase Inc.

MS SQL Server is a current company standard and competes with SYBASE in the Client/Server DBMS market Because of this we have no guarantee future versions of Powerbuilder will “play well” with our current version SQL Server.

Score: 60 Economic Feasibility

Cost to develop:

Payback period (discounted):

Net present value:

An assessment of how long the solution

will take to design and implement.

10% Less than 3 months.

Trang 38

 Applicable Techniques

 The following techniques are applicable to this activity

• Fact Finding Fact finding methods are used obtain costs,

opinions, and other facts about candidates from a variety of sources.

• Feasibility Analysis The ability to perform a feasibility

assessment is an extremely important skill requirement

Trang 39

• Step 1 - Obtain all product cost information for each product.

• Step 2 - Discuss candidate solutions with system owners and users to

obtain a feel for how well-received the solution would be from their perspectives.

• Step 3 - If possible, obtain feedback from customers who own or

have used the hardware and software product(s)

• Step 4 - Determine what economic measures to use to conduct the

cost-benefit feasibility analysis

• Step 5 - Evaluate each candidate solution independently for

operational, technical, economic, and schedule feasibility Document your analysis of each candidate solution.

Trang 40

consideration

remaining, we will identify and recommend the candidate that offers the “best overall” combination of technical, operational, economic, and schedule feasibilities

that a given candidate is found to be the most operational, technical, economic, and schedule feasible

Định dạng
Số trang	119
Dung lượng	858 KB