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					     ITEC 3010 “Systems Analysis and Design, I”

           LECTURE 2:
Approaches to System Development




                 [Prof. Peter Khaiter]            1
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                                 2
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 SDLC3
Predictive vs. Adaptive Approach
to the SDLC




                                   4
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

                                                  5
Systems Development Life Cycle




                                 6
Systems Life Cycle




                     7
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
                                    8
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
                                                           9
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
                                                 10
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   11
Implementation Activities


   Construct software components
   Verify and test
   Convert data
   Train users and document the
    system
   Install the system

                                    12
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         13
FIGURE 2-2 The
SDLC Phases.
            14
“Waterfall” Approach to the SDLC




                                   15
“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

                                           16
Overlap of activities




                        17
“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.
                                                                                         18
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



                                                    19
The Parallel Model




                     20
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
                                                21
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
                                                          22
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          23
The Spiral Life Cycle Model




                              24
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


                                                                   25
Iteration of System Development
Activities




                                  26
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
                                                              27
Phased Model




               28
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.

                                              29
Just For Fun

           http://www.funnyhumor.com/pictures/206.php




                                                        30
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.
                                                       31
Prototyping SDLC




                   32
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.
                                                       33
    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
                                                                     34
Throwaway Prototyping Model




                              35
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.


                                           36
Criteria for Selecting the
Appropriate Model of SDLC




                             37
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.
                                                                                      38
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.




                                                                                       39
Methodologies


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




                                              40
Relationships Among Components
of a Methodology




                                 41
Models


   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

                                                        42
Some Models Used in SDLC




                           43
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




                                             44
Some Tools Used in SDLC




                          45
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




                                             46
Some Techniques Used in SDLC




                               47
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                            48
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)‫‏‬


                                               49
Three Structured Programming
Constructs




                               50
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
                                          51
Top-Down or Modular Programming




                              52
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
                                                53
Structure Chart Created Using
Structured Design Technique




                                54
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                           55
Data Flow Diagram (DFD) Created
Using Structured Analysis
Technique




                              56
Entity-Relationship Diagram (ERD)
Created Using Structured Analysis
Technique




                                57
Structured Analysis Leads to
Structured Design and Structured
Programming




                                   58
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.                 59
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)                                                    60
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


                                                     61
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

                                                       62
Object-Oriented Approach to
Systems




                              63
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                                       64
Class Diagram Created During OO
Analysis




                              65
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
                                                          66
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
                                                                      67
Current Trends in Development


   More adaptive approaches
      The Unified Process (UP)‫‏‬
      Extreme Programming (XP)‫‏‬
      Scrum
   Details on each in Chapter 17




                                    68
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
                                                               69
Unified Process Life Cycle




                             70
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                         71
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


                                                         72
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

                                                   73
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
                                                         74
Visual Modeling Tool Repository
Contains All System Information




                                  75
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.
                                           76
Visio for drawing a variety of
diagrams and charts




                                 77
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                                            78
Oracle Designer: Front Panel
screen




                               79
Oracle Designer: Entity-
Relationship Diagrammer




                           80
 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             81
Together showing a class diagram
with synchronized Java source code




                                82
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)

                                    83
Embarcadero Describe with visual
modeling and round-trip
engineering




                                   84
                     Readings


Today’s lecture: Chapter 2 – “Approaches to
System Development”


For next lecture: Chapter 3 – “The Analyst as a
Project Manager”




                                                  85

				
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