The Systems Development Life Cycle SDLC

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

• A series of steps completed over a period of time
  by analysts in a system development or
  maintenance project.

3
System Life Cycle

• Embodies the entire life span of a system. In
  this text, life cycle will refer to project life
  cycle, unless indicated otherwise.

4
(No Transcript)
5
Logical and Physical Design

• The logical design provides the user's view of
  the system, while physical design specifies the
  actual way the system will be implemented.
• Logical design specifies the desired logical
  assembly of the system relative to what it will
  do and why, while physical design specifies how
  to physically implement the logical design.

6
Frederick Taylor's Scientific Management to
Solving Problems

• Define the Problem.
• Identify Alternative Solutions.
• Evaluate the Alternatives.
• Implement the Selected Alternative Solution.

7
System Development and Maintenance Life Cycle

• Problem Definition.
• System Analysis and Feasibility Study.
• System Design.
• System Development.
• System Testing.
• Installation, Conversion, and Training.
• Formal Review.
• System Modification and Enhancement.
• Maintenance.

8
Problem Definition

• Problem definition is performed by the analyst to
  identify the central purpose for the SAD project.

9
Types of Problems

• Omission.
• Addition.
• Modification.
• Deletion.

10
System Project Request

• The problem usually comes to the attention of the
  systems analysis staff either through a formal
  systems request or direct communication with
  affected users.

11
(No Transcript)
12
Feasibility Study

• A study to determine if a systems analysis and
  design project is both operationally and
  economically feasible. A more detailed
  operational/economical feasibility study is
  performed as more information is acquired
  concerning the project.

13
Operational Feasibility

• Refers to having a project that can be completed
  operationally, or completing a system project
  that develops a system that the company can
  operationally support.

14
Economical Feasibility

• Refers to having a project that can be completed
  based on considering the financial costs of
  completing the project versus the benefits of
  completing it.

15
Documentation

• Creating detailed descriptions and explanations
  for all the components of systems and their use
  from the perspective of both a designer/developer
  and a user.

16
System Analysis andDesign Documentation

• Designer/developer documentation which provides a
  "bird's-eye" view of the system to allow the
  project team to track the development of the
  project. This documentation becomes a permanent
  record for the completed system. All facts
  gathered and recorded become part of the
  development.

17
User Documentation

• A general explanation of the system.
• Detailed explanations of what is required of
  users in employing the system.
• Detailed explanations of the results of system
  executions.

18
User Requirements Documentation

• Documenting the information needs of people in
  the business produces the user requirements from
  which systems are constructed.

19
User Requirements using E/RD and DFD Modeling
Methods

• Are one way to standardize the creation of user
  requirements.
• By standardizing the creation of user
  requirements and other system documentation, a
  company makes it easier for someone with
  knowledge of one system to gain a working
  knowledge of another.

20
Design Dictionary

• A comprehensive collection of the design
  specifications used to define and describe all
  the components specified in designing a system.
• The design dictionary becomes an extremely
  valuable source of information because it permits
  another analyst to gain comprehensive knowledge
  of the system.

21
Three Basic Alternativesto Solving the Problem

• Modify the existing system.
• Replace the existing system by developing a new
  system.
• Replace the existing system by purchasing a new
  system.

22
Replacing the Existing Systemby Developing a New
System

• No software vendor supplies a system of the type
  needed.
• An appropriate vendor-supplied system is deemed
  too costly.
• A vendor-supplied systems would require far too
  much customization for it to match the needs of
  the users.
• The firm does not have the available staff
  required to complete the system project.

23
Replacing the Existing System by Purchasing an
Available Vendor-Supplied System

• An existing vendor-supplied system will cost
  effectively meet user's needs, and
• The firm does not have available staff to
  complete the project.

24
Three Alternative Perspectives that Existfor
Each of the Three Alternative Solutions

• The pessimistic (conservative) solution.
• The most likely (middle of the road) solution.
• The optimistic (liberal) solution.
• These solutions suggest answers to the "what if"
  questions that assume either
• The worst possible outcome.
• The most likely outcome.
• The best possible outcome.

25
Logical Design

• Consists of a logical series of operations
  necessary to meet user's new or additional
  information needs with little regard for physical
  implementation.
• Logical design focuses on WHAT the user needs
  with little, if any, consideration for HOW that
  need can be met through physical circumstances.

26
Logical Design Models

• During logical design, the analyst often creates
  a model of the proposed system that shows the
  user what the system will look like, what it will
  do, and what outputs it will generate.

27
Physical Design

• Embodies an expansion of the logical design that
  includes the details of software and hardware
  that give physical reality to the logical design.
• Physical design is devoted to creating
  specifications that establish the physical
  environment within which the system will operate,
  the physical characteristics of the system, and
  how it will physically function.

28
Steps in Physical Design

• Identify resources needed to meet user needs.
• Identify procedures necessary to meet user needs.
• Describe the procedures so that computer code can
  be generated.
• Describe data so that stored data can be created
  or modified.
• Identify additional technology necessary for the
  new or modified system.

29
System Development(Design Implementation)

• Involves creating the separate modules that
  compose the system consists and their integration
  with other software into a harmonious system.

30
Structured Analysis and Design

• Dictates that modules be designed and developed
  as separate components that are integrated to
  produce a harmoniously performing system through
  the creation of various interfaces, the sharing
  of data, and limited task sharing.

31
System Testing

• Testing the separate modules and the integrated
  system.
• Types of Testing
• Syntactical errors.
• Logical errors.
• Path testing.

32
Types of Errors

• Syntax Errors
• Occur when a programmer does not follow the rules
  (grammar) of the specific software language or
  they misspell or misuse key-words (vocabulary) of
  the language.
• Logical Errors
• Occur if the output does not precisely conform to
  the requirements specified for that component of
  the system, even though the program passes all
  syntactical checks.
• Path Testing
• Involves testing all of the logical procedures
  through a program's logic.

33
System Implementation Activities

• System installation.
• Conversion.
• Training.

34
Installation - Conversion - Training

• All have a transitional nature they transition
  into having the system in production, conversion
  of data, storage, etc., and training on the use
  of the new system and accompanying practices and
  technology.

35
System Installation

• Immediate change-over.
• Phased change-over.
• Parallel execution.
• Pilot execution.

36
Conversion

• The practice of modifying existing data, data
  storage, software, and hardware to fit a newly
  modified or developed system.

37
Reusable Code

• Refers to existing software modules that can be
  reused in new or modified systems, although they
  often need conversion into a new format.

38
Training

• Essential if they are to use these new system
  acquisitions effectively.
• Usually involves both in-house courses and
  external seminars.
• Includes how to use the new system and interpret
  its output.
• New systems require users to become acquainted
  with screen-formatted data entry, responses to
  system generated screen prompts, and new
  reporting methods.

39
System Project Formal Review

• Consists of upper-level and lower-level
  management and system professionals responsible
  for evaluation of project results.

40
System Project Modificationand Enhancement

• New or modified systems usually some
  modifications and enhancements immediately
  following the formal review phase of the project.

41
System Maintenance

• Involves modifying the design of the system and
  developed programs to provide for the needs of
  the users.
• Although system maintenance may not be considered
  a part of the SDLC, it is a part of the life
  cycle of a system.

42
SDLC - Logical and Physical Modeling - Modeling
Methods

• Life Cycle Phase Logical/Physical Modeling
  Methods
• Problem definition Logical Analysis
  modeling methods
• System analysis and Logical Analysis
  modeling methods
• feasibility study
• Logical design Logical Logical modeling
  methods
• Physical design Physical Physical
  modeling methods
• Development Physical Physical modeling
  methods
• System testing Physical Physical
  procedures
• Installation conversion Physical Physical
  procedures
• and training
• Formal review Physical Physical
  evaluation
• System modification Logical/Physical
  Logical/Physical modeling
• and enhancement methods/procedures

43
System Project Management

• Using project management principles to manage the
  significant amount of the firm's resources
  (personnel, materials, facilities, etc.)
  mobilized by an AD project in the most efficient
  and valid manner.
• Project Master Schedule
• A schedule used to track the actual completion
  of portions of the project.

44
Types of System Projects

• Reactive System Development Project
• A project that originates as a reaction to
  changes in the business environment.
• Proactive System Development Project
• A project that anticipates positive
  modifications in the firm's operations and
  systems that are planned by key personnel in the
  firm.