SYSTEMS DESIGN AND ANALYSIS

1. 2. The Systems
Development Life Cycle
(SDLC)

2. The System Development Life
Cycle
It was started in the 1960s and 1970s as the first
documented approach to computer systems
development. All the stages of the development
system are thought about, planned, monitored
and Completed. SDLC is the process by which an
Information System comes to life and maintains
its usefulness to a business as it moves from
inception to replacement.

3. Business need - changing business
conditions prompt request for
new/improved computer system
System development - analyse, design
and implement a system to meet the
business need
System installation - move new system
into production
System Development Life
Cycle

4. System operation - period of active
use
System obsolescence - system no
longer reflects changed business
needs
System Development Life
Cycle

5. Need
Develop
Install
Operate
Obsolete
System Life Cycle - illustration

6. Critical Success Factors for Systems
Development:
effectively meet the stated business needs
build a flexible and maintainable system
build a reliable system
produce a system on time and within
budget
System Development
Challenges

7. The phases of the SDLC are described
Differently depending on the author:
Kendall & Kendall terminology
Shelly terminology
Powers et al terminology
Etc.
Terminologies for the SDLC phases

8. Investigation
 Identify problems and opportunities
Determine requirements
Analysis
Design
Develop software
System Test
Implement and evaluate
System Development Life Cycle
(Kendall & Kendall terminology)

9. System Development Life Cycle
(Kendall & Kendall terminology)

10. Systems planning
Preliminary investigation report
Systems analysis
System requirements document
Systems design
System design specification
Systems implementation
Complete functioning information system
Systems operation and support
Operational information system
Systems Development Life Cycle
(Shelly terminology)

11. SDLC – (Shelly terminology)
.

12. Systems planning
Purpose – identify problem’s nature/scope
Systems request – begins the process &
describes desired changes/improvements
Systems planning – includes preliminary
investigation or feasibility study
End product – preliminary investigation report
Systems Development Life Cycle

13. Systems analysis
Purpose is to learn exactly how the current
system operates
Fact-finding or requirements
determination is used to define all
functions of the current system
Systems Development Life Cycle

14. Options
Develop a system in-house
Purchase a commercial package
Modify an existing system
Stop development
The end product for this phase is the systems
requirements document
Systems Development Life Cycle

15. Systems design
Purpose is to satisfy all documented
requirements
Identify all outputs, inputs, files, manual
procedures, & application programs
Avoid misunderstanding through manager and
user involvement
End product is system design specification
Systems Development Life Cycle

16. Systems implementation
Construct/deliver information system
Prepares functioning, documented system
Write, test, document application programs
User and manager approval obtained
File conversion occurs
Users, managers, IS staff trained to operate and
support the system
Post-implementation evaluation performed
Systems Development Life Cycle

17. Systems operation and support
New system supports business operations
Maintenance changes correct errors or meet
requirements
Enhancements increase system capability
After several years of operation, systems
experience need for extensive changes
Systems development life cycle ends with
system replacement
Systems Development Life Cycle

18. 2. Determine requirements
3. Analysis
4. Design
5. Develop software
1. Investigation -
Identify problems,
opportunities
6. System Test
7. Implement
and evaluate
System Development Life Cycle illustration

19. Many organisations and many authors
use different terminology for the phases
of the SDLC
However essentially the same activities
are performed
Refer to examples of other terminology
Other Terminology for SDLC phases

20. Investigation phase
Analysis and General Design phase
Detailed Design and Implementation
phase
Installation phase
Review phase
System Development Life Cycle
(Powers et al terminology)

21. Initial investigation
Feasibility study
Financial feasibility
Technical feasibility
Operational feasibility
Legal /ethical feasibility
Investigation phase

22. Existing system review
 build model of existing system
New system requirements
 from User’s point of view
New system design
 sufficient information for management to decide
whether to proceed
Implementation and Installation planning
 plan to cover next phases
Analysis and General Design phase

23. Technical design
 for programs (pseudo-code), files, records,
reports, screens
Test specifications and Testing
prepare test plans
Programming and Testing
 write and test program code
User Training
System and Acceptance test
 by Users, simulating production conditions
Detailed Design and Implementation
phase

24. File conversion
 run programs to convert files into new format
System installation
 critical system transition to production
Options for installation are:
 Cutover can be abrupt
 Operate old and new systems in parallel
(for 2 weeks)
 Phase in new system, over time
 Install version of the system
Installation phase

25. Development recap
 team review of project, for benefit of
future projects
Post implementation review
 evaluate how well the system is working
 to what extent are project benefits being
achieved?
Review phase

26. Business Survey
Feasibility
Systems Analysis
Systems Design
Programming
Testing
Implementation
Post Implementation Review
Maintenance
S D L C Phases (general)

28. Management needs to know:
project is on time
project is within budget
These project control stages
(checkpoints) are the end of each
phase of the System Development Life
Cycle
Why have a System Development Life Cycle?

29. Initial broad term report
Estimate:
project cost
project resources (people)
project time
Recommend whether go on to
Feasibility
1. Business Survey

30. Assess feasibility of the project:
operational feasibility
technical feasibility
financial feasibility
Identify possible solutions and options
Recommend most appropriate to
management
Outline of development plan
2. Feasibility

31. Information Gathering
User Requirements refined to
specify the new system
Goal - User Requirements Document
 design for the new system
 just enough technical detail
for the customer
Report contents geared towards
customer
3. Systems Analysis

32. Convert User Requirements into
computer terms
Specify
how system will operate
what programs are needed
what the programs will do
4. Systems Design

33. Convert specifications into program
code
Prepare test plans
 for unit testing (individual programs)
5. Programming and Design Aim

34. Design aim must ensure that the
system is:
 Accurate • Implementable
 Maintainable • Acceptable
 Timely • Flexible
 Robust • Economic
 Efficient • Secure
 Compatible • Portable
5. Programming and Design Aim

35. System Testing & Acceptance
Testing
System Testing
test program as part of the whole
system e.g. new program in whole
payroll system
6. Testing - make system “bullet
proof”

36. Acceptance Testing
Customers / Users now involved
usually have their own test plans
sometimes also use programmer
tests
Sign-Off document - signed by
Customer Coordinator
6. Testing - make system “bullet
proof”

37. Implementation Plan or Update Log
Provides project leader with a list of all:
files - new / amended
screen messages - new / amended
programs (sources) - new / amended
Timing for lodgment in production
environment decided with customer
7. Implementation

38. BUILDING of the system is now complete
Development recap
 team review - what can be learned from the
project
Post Implementation Review (after 3 or 4
months)
 degree to which system meets objectives
 often results in recommended improvements
8. Post Implementation
Review

39. Ensure customer changes to the system:
 retain quality
 adhere to standards and procedures
Now back at the beginning of the SDLC
Size of maintenance change will
determine whether all (or subset of)
phases of the system Development Life
Cycle are required
9. Maintenance

40. Life-Cycle Models
1. The waterfall model
2. The spiral model
3. Rapid application development
4. Joint application development
5. The V model

41. Each Phase of SDLC has an
“Output”
Phase
• Requirements analysis
• Design
• Implementation
• Test
Output
• Software Requirements
Specification (SRS),
• Design Document,
Design Classes
• Code
• Test Report,
Change Requests

42. “Life-Cycle” Models
Single-Version Models
Incremental Models
Single-Version with Prototyping
Iterative Models

43. “Life-Cycle” Models (1)
Single-Version Models
Waterfall Model
 Waterfall Model with “back flow”
“V” model: Integrating testing

44. Incremental vs. Iterative
These sound similar, and sometimes are
equated.
Subtle difference:
 Incremental: add to the product at each phase
 Iterative: re-do the product at each phase
Some of the models could be used either way

45. The waterfall model
First described by Royce in 1970
There seem to be at least as many
versions as there are authorities -
perhaps more
The Waterfall model

46. Waterfall Model
Requirements
Design
Implementation
Test
Each phase “pours over” into
the next phase.

47. Waterfall Model
Managers love waterfall models:
Nice milestones
No need to look back (linear system), one
activity at a time
Easy to check progress : 90% coded, 20%
tested

48. Waterfall Model
Traditional life cycle
Analysis, design, code, test & maintenance
Top down rigidity
No iteration between phases
Difficult accommodating uncertainty & risk
Black box approach

49. Why Not Waterfall?
2. Requirements are not stable/unchanging.
The market changes—constantly.
The technology changes.
The goals of the stakeholders change.

50. Why Not Waterfall?
3. The design may need to change during
implementation.
Requirements are incomplete and changing.
Too many variables, unknowns, and novelties.
A complete specification must be as detailed as code itself.
Software is very “hard”.
 Discover Magazine, 1999: Software characterized as the most
complex “machine” humankind builds.

51. V - Model
The V Model Distinguishes
between Development and
Verification Activities

52. V - Model
Each phase has corresponding test or validation counterpart
Requirements
Analysis
System Design
Program Design
Implementation
Unit Test
Integration
Test
Acceptance
Test

53. V - Model
Level of Detail
Project Time
Low
High
Acceptance
Testing
Problem with V-Model:
Client’s Perception is the same as the
Developer’s Perception
Client’s Understanding
Developer’s Understanding
Requirements
Elicitation
Analysis
Design
System
Testing
Object Design Unit Testing
Integration Testing

54. Problems with V - Model
The V model does not model iteration

55. Boehm Spiral Model
Four major activities
1. Determination of objectives, alternatives,
and constraints
2. Risk analysis and prototyping
3. Waterfall approach to next level product
4. Plan for the next phase cycle:

56. Boehm Spiral Model

57. Identify risks
Assign priorities to risks
Develop a series of prototypes for the identified risks
starting with the highest risk.
Use a waterfall model for each prototype
development (“cycle”)
If a risk has successfully been resolved, evaluate the
results of the “cycle” and plan the next round
If a certain risk cannot be resolved, terminate the
project immediately
Spiral Model Deals with Iteration

58. Limitations of the Waterfall
and Spiral Models
Neither of these model deals well with
frequent change
 The Waterfall model assume that once you are
done with a phase, all issues covered in that
phase are closed and cannot be reopened
 The Spiral model can deal with change between
phases, but once inside a phase, no change is
allowed
What do you do if change is happening more
frequently? (“The only constant is the
change”)

59. Rapid Application
Development
RAD is a methodology for compressing
the analysis, design, build, and test
phases into a series of short, iterative
development cycles.
This has a number of distinct
advantages over the traditional
sequential development model.

61. Rapid Application Development
Iteration allows for effectiveness and
self-correction.
Iterations results into many small
refinements and improvements.
An important, fundamental principle of
iterative development is that each
iteration delivers a functional version of
the final system

62. Rapid Application Development
Like prototyping, uses iterative
development
Uses tools to speed up development
 GUI
 reusable code
 code generation
 programming, language testing and debugging

63. Rapid Application Development
RAD projects are typically staffed with small
integrated teams comprised of developers,
end users, and IT technical resources.
Small teams, combined with short, iterative
development cycles optimizes speed, unity of
vision and purpose, effective informal
communication and simple project
management.

64. Rapid Application Development
High Speed
High Quality
And Lower Cost
Quality is a primary concept in the RAD
environment. Systems developed using
the RAD development path meet the
needs of their users effectively and
have low maintenance costs.

65. Preliminary working version of a system (or
one of its parts)
built quickly and inexpensively
using “friendly, powerful” software
reviewed by end users
suggest changes for system improvements.
Prototyping

66. Iterative process, say 10 versions
Result - evolve to become final system, or
... throw away, but clarified SDLC
requirements
Prototyping

67. Identify Basic User RequirementsIdentify Basic User Requirements
Rapidly Develop PrototypeRapidly Develop Prototype
Users work with PrototypeUsers work with Prototype
Obtain User FeedbackObtain User Feedback
Modify the PrototypeModify the Prototype
IterativeIterative
enhancementenhancement
ThrowawayThrowaway
PrototypePrototype
EvolutionaryEvolutionary
PrototypePrototype
Prototyping Process

68. Prototype
Steps followed by a systems
analyst using a prototype during
the systems analysis phase are
shown

69. Prototype
*

70. Prototyping can help to obtain complete
and reliable system requirements
Prototyping process:
iterative
User works with latest version of prototype
to determine the refined requirements
prototype quickly amended (by the User
and systems analyst)
Prototyping

71. Interactive software development tools
Allows designer to quickly:
design screens, create files, data entry
routines,
basic reporting functions
Tools should be flexible and easy to use
Prototyping tools

72. Prototyping goal is to enhance the System
development process. Prototyping focuses
on the Analysis and General Design
phase.
Outcome –
 one extreme is prototype actually becomes the
finished system (after many iterations)
 other extreme is throw away prototype and
build system using conventional methods
 BUT now have very high level of confidence
with accuracy and completeness of User
Requirements
Prototyping and the SDLC

73. Prototyping
Performing analysis, design, and
implementation phases concurrently,
and repeatedly
Users see system functionality quickly
and provide feedback
Decision maker learns about problem
But can lose gains in repetition

74. Prototyping
Design
Implementation
Analysis
Need
Planning
Prototype
System
Prototype Not OK
Prototype OK

75. Uses of Prototyping
Verifying user needs
Verifying that design = specifications
Selecting the “best” design
Developing a conceptual understanding of novel
situations

76. Uses of Prototyping
Testing a design under varying environments
Demonstrating a new product to upper
management
Implementing a new system in the user
environment quickly

77. Prototyping
Proposed Advantages
Improved user
communication
Users like it
Low risk
Avoids over-design
Experimentation
and innovation
Spreads labor to
user department
Disadvantages in practice
 Prototypes are used “as is”
 Integration often
difficult
 Design flaws
 Poor performance
 Difficult to manage process
 Creates unrealistic
expectations
 Documentation is difficult

78. Advantages of Prototyping
Short development time
Short user reaction time
Improved user understanding
Low cost

79. Disadvantages of Prototyping
Gains may be lost in
Thorough understanding information
System’s benefits and costs
Detailed description of information needs
Easy to maintain IS design
Well-tested IS
Well-prepared users

80. Alternative methodologies to SDLC are:
Structured approaches.
 Structured System Analysis & Design
Methodology
 Yourdon
 Jackson system development
 Merise
 Work flow systems
Prototyping.
Alternative system development
methodologies

81. Alternative methodologies to SDLC are:
Joint Application Development
Rapid Application Development
Object oriented analysis and design.
Soft Systems Methodology.
Alternative system development
methodologies

82. JAD
Joint application development (JAD)
 Task force of users, managers, and IS staff
 Objectives
 Gather information
 Discuss business needs
 Define the new system requirements
 Methods
 Team usually meets at specific location
 Team has project leader and recorder(s)
 Key users participate in intense development effort
 JAD can be costly, but highly effective
Package
Click to see Figure 3-11

83. RAD
Rapid application development (RAD)
 Team method similar to JAD, but goes further
 RAD phases resemble a mini-SDLC
 Requirements planning, user design, construction, and
cutover
 RAD involves a continuous design process
 Team can react quickly
 Final objective is a functioning system
 RAD can be faster and less costly, but stresses
system mechanics rather than strategic needs

84. OOAD
Object-oriented (O-O) systems development
 Object-based model
 Objects and their attributes are abstract entities
 Classes and subclasses

85. Review Questions
1. List and describe the major stages of the
systems development life cycle.
2. What is prototyping and what
advantages does it offer in the SDLC?
3. Explain why the investigation phase and
the initial analysis and design phases are
perhaps the most critical stages of the
SDLC.
4. Explain the systems life cycle and
describe why this concept is important to
systems developers.

86. BUT
Soft Systems Methodology.