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Approaches to System Development

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Presentation on theme: "Approaches to System Development"— Presentation transcript:

1 Approaches to System Development
Lecture 2

2 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

3 Some Models Used in System Development Figure 3-1

4 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

5 Some Tools Used in System Development Figure 3-2

6 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

7 Some Techniques Used in System Development Figure 3-3

8 Components of a Methodology Figure 3-4
Relationships Among Components of a Methodology Figure 3-4

9 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)

10 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

11 DFD Created Using the Structured Analysis Technique Figure 3-8

12 Structured Analysis Figure 3-9
ERD Created During Structured Analysis Figure 3-9

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

14 Beginning the Analysis:
Investigating System Requirements

15 Analysis Phase in More Detail Figure 4-1

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

17 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

18 Stakeholders People with interest in system success
Three primary groups Users (use system) Clients (pay for system) Technical staff (ensure system operation)

19 Users as Stakeholders User roles Business users Information users
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

20 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

21 Information Gathering and Model Building
Figure 4-5

22 Themes for Information-Gathering Questions
Figure 4-6

23 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

24 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

25 Conduct Interviews and Discussions with Users
Most effective way to understand business functions and rules Time-consuming and resource-expensive May require multiple sessions

26 Sample Interview Checklist Figure 4-8

27 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

28 Characteristics of Prototypes
Preliminary working model of a larger system Operative Working model Focused Accomplishes single objective Quick Can be built and modified rapidly

29 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

30 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

31 Evaluating the options for an IS (making the decision)

32 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

33 Business System Options
Project Initiation Document Logical DFM Requirements Catalogue Stage 2 Business System Options Define BSOs 2 - 6 BSOs each containing: description of functions & Users scope cost benefit analysis impact analysis Select BSOs chosen Business System Option Requirements Specification

34 Range of Options Dramatic options No change option Other possibilities
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

35 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

36 BSOs must be easily understood by users
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

37 Example - Yorkies Option 1 Centralised 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.

38 Centralised System DFD
Booking Confirmation Make Booking Depot Completed Bookings Booking Details Maintain Vehicle Records Record Completed Booking

39 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)

40 Autonomous Local Offices Partial DFD
Customers Sales Customer Customer Booking Information New Customer HO/Comp Customer Information LO/Comp Maintain Customer Records LO/Comp Make Booking for Own Office New credit Receiving rating Office Arrange One-way Hire Vehicle Availability Finance Booking Bookings Vehicle Arriving Booking Vehicle Availability at other offices Other Local LO/Comp Office Booking Request Booking at Nearby Office Local Offices Request Nearby Local Office LO/Comp = Local Office + Computer HO/Comp = Head Office + Computer

41 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.

42 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

43 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

44 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

45 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

46 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

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