1. LECTURE 2: Approaches to System Development
ITEC 3010 “Systems Analysis and Design, I”
LECTURE 2: Approaches to System Development
[Prof. Peter Khaiter]

2. Lecture Outline Systems Development Life Cycle
Phases and Activities in the SDLC
Variations of the SDLC models
Selecting the appropriate model
Methodologies of the SDLC
Traditional Approach to SDLC
Information Engineering Approach to SDLC
Object-Oriented Approach to SDLC
Rapid Application Development
Current trends in the SDLC
CASE Tools

3. Systems Development Life Cycle
Systems development life cycle (SDLC)‏
Provides overall framework for managing systems development process
Two main approaches to SDLC
Predictive approach – assumes project can be planned out in advance
Adaptive approach – more flexible, assumes project cannot be planned out in advance
All projects use some variation of SDLC

4. Predictive vs. Adaptive Approach to the SDLC

5. Phases in SDLC
Project planning – initiate, ensure feasibility, plan schedule, obtain approval for project
Analysis – understand business needs and processing requirements
Design – define solution system based on requirements and analysis decisions
Implementation – construct, test, train users, and install new system
Support – keep system running and improve

6. Systems Development Life Cycle

7. Systems Life Cycle

8. Activities of Each SDLC Phase
Predictive or adaptive approach use SDLC
Activities of each “phase” are similar
Phases are not always sequential
Phases can overlap
Activities across phases can be done within an iteration

9. Activities of Project Planning
Define business problem and scope
Produce detailed project schedule
Confirm project feasibility
Economic, organizational, technical, resource, and schedule
Staff the project (resource management)‏
Launch project  official announcement

10. Analysis Activities Gather information to learn problem domain
Define system requirements
Build prototypes for discovery of requirements
Prioritize requirements
Generate and evaluate alternatives
Review recommendations with management

11. Design Activities Design and integrate the network
Design the application architecture
Design the user interfaces
Design the system interfaces
Design and integrate the database
Prototype for design details
Design and integrate system controls

12. Implementation Activities
Construct software components
Verify and test
Convert data
Train users and document the system
Install the system

13. Support Activities (SLC, not SDLC)
Maintain system
Small patches, repairs, and updates
Enhance system
Small upgrades or enhancements to expand system capabilities
Larger enhancements may require separate development project
Support users
Help desk and/or support team

14. FIGURE 2-2 The SDLC Phases.

15. “Waterfall” Approach to the SDLC

16. “Waterfall” Approach
Each life cycle phase is completed in sequence and then the results of the phase flow on to the next phase
There is no going back once the phase is completed (like a waterfall) or it is extremely difficult to do
The key deliverables for each phase are typically produced on paper (hundreds of pages in length)
The decisions made at each phase are frozen, i.e. they cannot be changed

17. Overlap of activities

18. “Waterfall” Approach: pros and cons
The two key advantages of the waterfall model:
• Identifying system requirements long before programming begins
• It minimizes changes to the requirements as the project proceeds
The key disadvantages:
• The design must be completely specified on paper before programming begins
• A long time elapses between the completion of the system proposal in the analysis phase and the delivery of the system (usually many months or years).
• A paper document is often a poor communication mechanism, so important requirements can be overlooked in the hundreds of pages of documentation
• Users rarely are prepared for their introduction to the new system, which occurs long after the initial idea for the system was introduced.
• If the project team misses important requirements, expensive post-implementation programming may be needed.
• A system may require significant rework because of changes in business environment since the time the analysis phase occurred. It means going back to the initial phases and following the changes through each of the subsequent phases in turn.

19. The Parallel Model
The Parallel Model attempts to address the problem of long delays between the analysis phase and the delivery of the system.
Instead of doing the design and implementation in sequence, it performs a general design for the whole system and then divides the project into series of distinct subprojects that can be designed and implemented in parallel
Once all subprojects are complete, the final integration of the separate pieces is delivered

20. The Parallel Model

21. Parallel Model: pros and cons
Primary advantages:
Can reduce the schedule time required to deliver a system
There is less chance of changes in the business environment causing rework
Key disadvantages:
Still suffers from problems caused by paper documentation
A new problem: sometimes the subprojects are not completely independent; design made in one subproject may affect another and the end of the project may require significant integrative efforts

22. Newer Adaptive Approaches to the SDLC
Based on spiral model
Project cycles through development activities over and over until project is complete
Prototype created by end of each cycle
Focuses on mitigating risk
Iteration – Work activities are repeated
Each iteration refines previous result
Approach assumes no one gets it right the first time
There are a series of mini projects for each iteration

23. Spiral Model
Breaks each project into smaller pieces, each with a different type of risk (Sources of risk: undefined requirements, complex technology, uncertain competitive environment)
The project begins in the center of the spiral where project is still small, easy to manage and low in risk
Then the project slowly expands
The project starts out small, initially handling a few of the risks
Then the project expands in next iteration to address more of the risks
Eventually the system is completed (all risks addressed)
Advantage:
The iterative nature and focus on risk reduction

24. The Spiral Life Cycle Model

25. The Model with Iterations
Iteration: the process of looping through the same development activities multiple times, sometimes at increasing levels of details or accuracy
Assumes no one gets the right results the first time
Do some analysis, then some design, then some implementation, then do some further analysis, etc until you get it right
Idea: not always realistic to complete analysis before starting design
Waterfall no longer applies - Phases become blurred
Decisions are not frozen at the end of each phase
Applicability:
Good for projects where requirement specifications are hard to arrive at

26. Iteration of System Development Activities

27. Phased Development Model
Breaks the overall system into a series of versions that are developed sequentially
The analysis phase identifies the overall system concept. The project team, users and system sponsors categorize the requirements into a series of versions
The most important and fundamental requirements are bundled into the first version of the system. The analysis phase then leads into design and implementation, but only with the set of requirements identified for version 1
Once version 1 is implemented, work begins on version 2. Additional analysis is performed on the basis of the previously identified requirements and combined with new ideas and issues that arose from users’ experience with version 1.
Version 2 then is designed and implemented, and work immediately begins on the next version. This process continues until the system is complete

28. Phased Model

29. Phased Model: pros and cons
Advantages: Quickly getting a useful system into the hands of users. Although it does not perform all the functions the users need, it helps them sooner to identify important additional requirements
Disadvantages: The users begin to work with systems that are incomplete. It is critical to identify the most important and useful features and include them in the first version. 

30. Just For Fun

31. Prototyping model
Performs analysis, design and implementation phases concurrently, and all three phases are performed repeatedly in a cycle until the system is completed.
The basics of analysis and design are performed, and work immediately begins on a system prototype (i.e., a ‘quick-and-dirty” program that provides a minimal amount of features
The first prototype is shown to the users and the project sponsor, who provide comments, which are used to re-analyze, re-design, and re-implement a second prototype that provides a few more features
This process continues in a cycle until the analysts, users and sponsor agree that the prototype provides enough functionality to be installed and used. Refinement occurs until it is accepted as the new system.

32. Prototyping SDLC

33. Prototyping model: pros and cons
The key advantages:
• Very quickly provides a system for users to interact with. It reassures the users that the project team is working on the system. The users can interact with the prototype to better understanding what it can and cannot do rather than attempting to understand a system specification on paper.
The major disadvantages:
• Fast-paced system releases challenge attempts to conduct careful, methodical analysis. Often the prototype undergoes such significant changes that many initial design decisions become poor ones. This can cause problems in the development of complex systems because fundamental issues and problems are not recognized until well into the development process.

34. Throwaway Prototyping
Similar to the prototyping model in that it includes the development of prototypes, however, they are done at a different point in the SDLC
Has a relatively thorough analysis phase that is used to gather information and to develop ideas for the system concept. Many of the features suggested by the users may not be well understood and many technical issues may not be solved.
Each of these issues are examined by analyzing, designing and building a design prototype (it is not a working system; it only represents a part of the system that needs additional refinement and it contains only enough details to enable users to understand the issues under consideration)
Typically, several prototypes are used during analysis and design phase. Each of them is used to minimize the risk of missing of important issues before the real system is built.
Once the issues are resolved, the project moves into design and implementation. At this point, the design prototypes are thrown away, what is a principal difference between this model and prototyping, in which the prototypes evolve into the final system

35. Throwaway Prototyping Model

36. Throwaway Prototyping: pros and cons
• Balances the benefits of well-through-out analysis and design phases with the advantages of using prototypes to refine key issues before a system is built.
• It may take longer to deliver the final system as compared with prototyping (as far as the prototypes do not become the final system), but this model usually produces more stable and reliable systems.

37. Criteria for Selecting the Appropriate Model of SDLC

38. Criteria for Selecting
Clarify of user requirements Sometimes the user requirements are unclear or subject to change. Prototyping and throwaway prototyping are more appropriate models for such situations, because they provide prototypes for user to interact with at early stages of the SDLC.
Familiarity with Technology When the system will use new technology, which is unfamiliar for the analysts and programmers (e.g. the first Web-based project with Java), it increases the risks. Application of the new technology as early as possible will improve the chance of success. Throwaway prototyping is particularly appropriate for this situation since it explicitly encourages the developers to develop design prototypes for areas with high risks. Phased model is good as well because it creates opportunities to investigate the technology in some depth before the design is complete.
System Complexity Complex systems require careful and detailed analysis and design. Throwaway prototyping is particularly well suited to such situation, but prototyping is not. The traditional structured methodologies can handle complex systems, but without the ability to get the system or prototypes into users’ hands early on, some key issues may be overlooked. Even though the phased model enables users to interact with the system early in the process.

39. Criteria for Selecting
Short time schedules Projects with short time schedules are well suited for RAD models as far as they are designed to increase the speed of development. Prototyping and phases development are excellent choices because they best enable the project team to adjust the functionality in the system. If the project schedule starts to slip, it can be readjusted by removing functionality from the version or prototype under development. The waterfall model is the worst choice, because it does not allow for easy schedule changes.
Schedule visibility One of the greatest challenges in systems development is knowing whether a project is on schedule. This is particularly true of the structured methods because design and implementation occur at the end of the project. The RAD models move many of the critical design decisions to an earlier point in the project to help project managers to recognize and address risk factors and keep expectations in check.

40. Methodologies Methodologies
Comprehensive guidelines to follow for completing every SDLC activity
Collection of models, tools, and techniques

41. Relationships Among Components of a Methodology

42. Models • physical (like a model of an airplane) Models
Representation of an important aspect of real world, but not same as real thing
Abstraction used to separate out aspect
• physical (like a model of an airplane)
• abstract (e.g. in form of mathematical notation or in graphical form)
Models in SDLC are graphical: diagrams and charts
Project planning and budgeting aids

43. Some Models Used in SDLC

44. Tools
Tools
Software support that helps create models or other required project components
Range from simple drawing programs to complex CASE tools to project management software

45. Some Tools Used in SDLC

46. Techniques Techniques
Collection of guidelines that help analysts complete a system development activity or task
Can be step-by-step instructions or just general advice

47. Some Techniques Used in SDLC

48. Two Approaches to System Development
Traditional approach
Also called structured system development
Structured analysis and design technique (SADT)‏
Includes information engineering (IE)‏
Object-oriented approach
Also called OOA, OOD, and OOP
Views information system as collection of interacting objects that work together to accomplish tasks

49. Traditional Approach Structured programming
Improves computer program quality
Allows other programmers to easily read and modify code
Each program module has one beginning and one ending
Three programming constructs (sequence, decision, repetition)‏

50. Three Structured Programming Constructs

51. Top-Down Programming
Divides complex programs into hierarchy of modules
The module at top controls execution by “calling” lower level modules
Modular programming
Similar to top-down programming
One program calls other programs to work together as single system

52. Top-Down or Modular Programming

53. Structured Design Technique developed to provide design guidelines
What set of programs should be
What program should accomplish
How programs should be organized into a hierarchy
Modules are shown with structure chart
Main principle of program modules
Loosely coupled – module is independent of other modules
Highly cohesive – module has one clear task

54. Structure Chart Created Using Structured Design Technique

55. Structured Analysis
Define what system needs to do (processing requirements)‏
Define data system needs to store and use (data requirements)‏
Define inputs and outputs
Define how functions work together to accomplish tasks
Data flow diagrams (DFD) and entity relationship diagrams (ERD) show results of structured analysis

56. Data Flow Diagram (DFD) Created Using Structured Analysis Technique

57. Entity-Relationship Diagram (ERD) Created Using Structured Analysis Technique

58. Structured Analysis Leads to Structured Design and Structured Programming

59. Weaknesses of the Structured Approach
• Techniques address some but not all of the activities of analysis and design
• Techniques make system development not enough formal (not like an engineering discipline) but rather like an art.
• The transition from the data flow diagram (in structured analysis) to the structure chart (in structured design) did not work well in practice.
• data modeling using structure chart and ER diagram were more important than modeling of processes (using dataflow diagrams)
• However, the structured approach overall still made processes rather than data the central focus of the system
• Many felt a strategic planning technique needed to be included in the approach to determine which systems to be built and to provide some initial requirements.
• As an alternative: information engineering.

60. Information Engineering (IE)‏
Focus on strategic planning to identify all the organization information needs (the application architecture plan), data modeling, and automated tools
More focused on data itself than the structured approach. But just as the structural approach includes data requirements, IE includes processes, too
The processing model of information engineering, the process dependency diagram, is similar to a data flow diagram, but it focuses more on which processes are dependent on other processes and less on data inputs and outputs
Provides more complete life cycle support through the use of an integrated CASE tools (help to automate systems development; final program code can be generated automatically by the CASE tools)
Became popular on large-mainframe systems in the 1980’s, less used in the 1990’s on smaller desktop systems (but concepts still used by planning and emphasis on data modeling)

61. Structured Approach and IE
Both approaches define information system requirements, design and construct information systems by looking at processes, data and the interaction of these two
Industry merged key concepts from structured development and information engineering approaches into traditional approach
An object-oriented technology provides a completely different perspective

62. Object-Oriented Approach
Completely different approach to information systems
Views information system as collection of interacting objects that work together to accomplish tasks
Objects – things in computer system that can respond to messages
Conceptually, no processes, programs, data entities, or files are defined – just objects
OO languages: Java, C++, C#, .NET, VB

63. Object-Oriented Approach to Systems

64. Object-Oriented Approach (continued)‏
Object-oriented analysis (OOA)‏
Defines types of objects users deal with
Shows use cases are required to complete tasks
Object-oriented design (OOD)‏
Defines object types needed to communicate with people and devices in system
Shows how objects interact to complete tasks
Refines each type of object for implementation with specific language of environment
Object-oriented programming (OOP)‏
Writing statements in programming language to define what each type of object does

65. Class Diagram Created During OO Analysis

66. SDLC Variations Many variations of SDLC in practice
Based on variation of names for phases
No matter which one, activities/tasks are similar
Some increase emphasis on people
User-centred design, participatory design
Socio-technical systems
Some increase speed of development
Rapid application development (RAD)‏
Prototyping

67. Rapid Application Development
Rapid application development (RAD) is one of the variations of SDLC
Aims to speed up the development process.
Emerged in the 1990s as an attempt to address both weaknesses of the waterfall development: long development times and the difficulty in understanding a system from paper-based description.
Methods:
• Tries to speed up the activities in each phase (e.g. speeding the analysis phase by scheduling intensive meetings of key participants to get information gathered and decisions made rapidly)
• Using iterative development (e.g., spiral life cycle model) to speed up the process of getting to design and implementation
• Building prototypes of the system during analysis and design phases. It improves understanding of the system requirements
• Using CASE (computer-aided system engineering) tools to speed up the analysis, design and implementation phases

68. Current Trends in Development
More adaptive approaches
The Unified Process (UP)‏
Extreme Programming (XP)‏
Scrum
Details on each in Chapter 17

69. The Unified Process (UP)‏
Object-oriented development approach
Offered by IBM / Rational
Booch, Rumbaugh, Jacobson
Unified Modeling Language (UML) used primarily for modeling
UML can be used with any OO methodology
UP defines four life cycle phases
Inception, elaboration, construction, transition
Defines workflows within each phase: business modeling, requirements modeling, analysis and design, implementation, testing, development, configuration and change management, and project management
Involves roles of: designer, use case specifier, systems analyst, implementer, architect

70. Unified Process Life Cycle

71. The Unified Process (UP) (continued)‏
Reinforces six best practices
Develop iteratively
Define and manage system requirements
Use component architectures
Create visual models
Verify quality
Control changes

72. Extreme Programming (XP)‏
Recent, lightweight, development approach to keep process simple and efficient
Describes system support needed and required system functionality through informal user stories
Has users describe acceptance tests to demonstrate defined outcomes
Relies on continuous testing and integration, heavy user involvement, programming done by small teams

73. Scrum For highly adaptive project needs
Respond to situation as rapidly as possible
Scrum refers to rugby game
Both are quick, agile, and self-organizing
Team retains control over project
Values individuals over processes

74. Computer-Aided System Engineering (CASE) Tools
CASE tools are software tools designed to help systems analyst complete development tasks
The CASE tool contains a database of information called a repository
The repository stores information about the system, including models, descriptions, and references that link the various model together
Information stored in repository can be used in a variety of ways by the development team
Every time a team member adds information about the system, it is immediately available for everyone else
CASE tools can check the models to make sure they are complete and follow the correct diagramming rules
CASE tools can check one model against another to make sure they are consistent

75. Visual Modeling Tool Repository Contains All System Information

76. CASE Tools: Examples Microsoft Visio
• a drawing tool suitable for about any system model
• comes with a collection of drawing templates (incl. symbols used in a variety of business and engineering applications: flowcharts, DFDs, ERDs, UML diagrams)
• provides only a limited repository for storing definitions and descriptions of diagram elements, but not a complete repository for a system development project.

77. Visio for drawing a variety of diagrams and charts

78. CASE Tools: Examples (cont’d)
Oracle Designer
• a tool set for recording definitions and automating the rapid constructions of flexible, graphical client-server applications
• integrated with Oracle Developer (a tool for creating GUI applications)
• includes a complete repository, diagramming and code-generating capabilities
• an integrated CASE tool that supports traditional approach to system development (process modeler, function-hierarchy diagrammer, data flow diagrammer, entity-relationship diagrammer)
• Design Transformer and Design Editor produce diagrams along with the database and application logic

79. Oracle Designer: Front Panel screen

80. Oracle Designer: Entity-Relationship Diagrammer

81. CASE Tools: Examples (cont’d)
TogetherSoft
• The most recent concept of round-trip engineering
• allows synchronizing the graphical models (such as class diagram) with generated program code (automation in both directions – round trip).
• If the program code is changed, the class diagram is updated and contra versa, if the class diagram is changed, the program code is updated.
• Together uses UML diagrams with several different programming languages

82. Together showing a class diagram with synchronized Java source code

83. CASE Tools: Examples (cont’d)
Embarcadero Describe
• a new product that include modeling and round-trip engineering features
• provides flexible UML modeling capabilities for analysis and design
• provides round-trip engineering with several Java development tools (JBuilder and Sum Forte)

84. Embarcadero Describe with visual modeling and round-trip engineering

85. Readings
Today’s lecture: Chapter 2 – “Approaches to System Development”
For next lecture: Chapter 3 – “The Analyst as a Project Manager”
Thank you !!!