1 Approaches to System Development Lecture 2. 2 Aids to Assist in Analysis and Design u Methodologies l Comprehensive guidelines to follow for completing.

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Approaches to

System Development

Lecture 2

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Aids to Assist in Analysis and Design

Methodologies Comprehensive guidelines to follow for

completing every SDLC activity Collection of models, tools, and techniques

Models Representation of an important aspect of the

real world Diagrams and charts Project planning aids

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Some Models Used in System DevelopmentFigure 3-1

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Aids to Assist in Analysis and Design

Tools Software support that helps create models

or other project components From simple drawing programs to complex

CASE tools

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Some Tools Used in System DevelopmentFigure 3-2

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Aids to Assist in Analysis and Design

Techniques Collection of guidelines that help analyst

complete system development activity or task Step-by-step instructions General advice

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Some Techniques Used in System Development

Figure 3-3

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Relationships Among Components of a Methodology

Figure 3-4

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Our approach to System Development

Traditional Approach Structured system development

Structured analysis Structured design Structured programming

Collectively referred to as structured analysis and design technique (SADT)

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Structured Analysis

Helps developer define what the system needs to do (processing requirements) Data to store and use Inputs and outputs How functions work together

DFDs and ERDs commonly show results of structured analysis

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DFD Created Using the Structured Analysis Technique Figure 3-8

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ERD Created During Structured Analysis

Figure 3-9

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Structured Analysis -> Structured Design -> Structured Programming - Figure 3-10

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Beginning the Analysis:

Investigating System

Requirements

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Analysis Phase in More DetailFigure 4-1

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Activities of the Analysis Phase/and Key Questions Figure 4-2

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Functional and Technical Requirements

System requirements – all capabilities and constraints

Functional requirements Activities the system must perform Based on procedures and business functions Documented in analysis models

Technical requirements Describes operating environment or performance

objectives Documented in narrative descriptions of technical

requirements

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Stakeholders

People with interest in system success

Three primary groups Users (use system) Clients (pay for system) Technical staff (ensure system operation)

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Users as Stakeholders

User roles Horizontal - information flow across departments Vertical - information needs of clerical staff,

middle management, and senior executives

Business users Information users Management users Executive users External users Client stakeholders Technical stakeholders

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Techniques for Information Gathering

Objective of analysis phase is to understand business functions and develop requirements

Original approach involved modeling of existing system

Current approach involves identifying logical requirements for new system

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Information Gathering and Model Building Figure 4-5

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Themes for Information-Gathering QuestionsFigure 4-6

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Fact Finding Methods

Review existing reports, forms, and procedure descriptions

Conduct interviews and discussion with users

Observe and document business processes

Build prototypes Distribute and collect questionnaires Conduct JAD sessions Research vendor solutions

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Review Existing Reports, Forms, and Procedure Descriptions

First technique in fact-finding

Purposes Preliminary understanding of processes Guidelines / visual cues to guide interviews

Identify business rules, discrepancies, and redundancies

Be cautious of outdated material

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Conduct Interviews and Discussions with Users

Most effective way to understand business functions and rules

Time-consuming and resource-expensive

May require multiple sessions

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Sample Interview Checklist Figure 4-8

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Observe and Document Business Processes

From office walkthrough to performing actual tasks

May make users nervous

Not necessary to observe all processes at same level of detail

May be documented with workflow diagrams

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Characteristics of Prototypes

Preliminary working model of a larger system

Operative Working model

Focused Accomplishes single objective

Quick Can be built and modified rapidly

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Distribute and Collect Questionnaires

Limited and specific information from a large number of stakeholders

Preliminary insight

Not well suited for gathering detailed information

Open-ended questions vs. close-ended questions

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Validating Requirements

Make sure gathered information is correct

Structured walkthrough Effective means of implementing quality

control early in project Verify and validate system requirements Review of findings from investigation and of

models based on findings

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Evaluating the options for an IS (making the decision)

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Business System Options

Take a fresh creative view of the required system Base options on the Requirements Catalogue Select best options for presentation to the user

two suggested for small projects six suggested for large projects

Express as narrative Supported as required with DFDs and LDS

users pick one (or a combination) option User selection promotes their ownership of the

system

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Business System Options

Project Initiation Document Requirements Catalogue Logical DFM

chosen Business System Option

Requirements Specification

Select BSOs

Users

Define BSOs

Stage 2 Business System Options

2 - 6 BSOs each containing: description of functions & scope cost benefit analysis impact analysis

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Range of Options

Dramatic options sack the salesmen and install terminals in customer’s offices

No change option do nothing and carry on with existing system

Other possibilities change responsibilities of staff perform functions in different places introduce technology to automate functions eliminate duplication increase usage of existing information improve communications between staff improve communications between company and customers

Position of system boundary

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Minimal and Advanced Options

Accommodate priorities defined in the Requirements Catalogue

Minimal option meets the mandatories of Requirements Catalogue may be an enhancement of current system

Advanced option meets all requirements “bells & whistles” solution high performance

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BSO Contents

Narrative describing functionality of system business priorities of system and constituent functions costs and benefits (may include full analysis) impact on users (organisation, structure, training) timescales for implementation any technical considerations affecting business system boundary and interfaces to other systems

(use DFD if appropriate)

BSOs must be easily understood by users

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Example - Yorkies Option 1Centralised System

Centralise all the control activities of the company depots only handle collection and return of vehicles.

Head office handles all bookings and invoicing. Drivers administered centrally

each driver only serves a group of nearby depots. Close local offices Post computer generated forms to customer/depot to confirm

bookings depots informed by telephone of changes

Mileage covered by the customer written on the booking form returned by depot to head office.

Depots inform head office of any vehicles out of service by telephone.

System requires a mini computer and approximately 35 terminals.

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Centralised System DFD

Make Booking

Record Completed

Booking

MaintainVehicle

Records

Bookings

Depot

Booking Confirmation

Completed Booking Details

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Example - Yorkies Option 2

Local Office Autonomy Local Office are responsible for their own

bookings, drivers, and invoicing Information held centrally - shared by all offices Almost all data is entered at the local offices Customers deal with theirlocal office for both

bookings and invoices Offices can make bookings at other offices if they

cannot be satisfied locally System requirements

mini computer and 55 terminals or PCs (1 per office) communications hardware and software about 52 printers (1 per office)

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Autonomous Local OfficesPartial DFD

Bookings

MaintainCustomer Records

Arrange One-way Hire

Request Bookingat Nearby Office

Booking

Vehicle Availability

Receiving Office

Booking

Booking Request

Vehicle Arriving

Nearby Local Office

Vehicle Availability at other offices

New credit rating

New Customer

Customer

Other Local Office

Finance

Sales

Booking

Local Offices

HO/Comp

LO/Comp

LO/Comp

LO/Comp

LO/Comp = Local Office + Computer

HO/Comp = Head Office + Computer

Customers

Customer Information

Customer Information

Make Bookingfor Own Office

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Autonomous Local Office DFD

Shows the distributed nature of the system head office responsible for the Customer

Records local offices responsible for the bookings.

Could draw separate DFDs for head office and local offices.

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Presentation of Business System Options

Depends on the project: may need report and formal presentations or just informal discussions

Prepare presentations list relative advantages and disadvantages of each

option refer to Requirements Catalogue

Make presentations Provide justifications for selection Record and document selection decisions

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Selection of a Business System Option

Users select one or a combination from the options presented

Record selection and reasons for choices Full specification will be developed for

selected BSO

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Yorkies Select Option 2 with Elements from other

Options Structure of the company remains the same No offices will be closed Information will be stored centrally on a mini

computer Each Local Office will have

a terminal or PC (to be decided at Stage 4) printing facilities

Head Office will control customer records and invoicing

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Selected Option (continued)

No terminals will be installed in the Depots Depots will use printed booking forms originated

by adjacent office Local Offices will

accept bookings for any office maintain customer records (except financial data) validate bookings against the customer records.

Drivers will be organised into regional pools Each driver will be available to any office in his

region

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Summary

Take a fresh creative view of the required system Base options on the Requirements Catalogue Select two or three options for presentation to the

user Present options as narrative describing

functionality, costs, benefits, and organisational impacts

Support presentation with LDS and DFDs if appropriate

Users pick preferred option or combination of options