chap1 sdlc
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THE SYSTEMSTHE SYSTEMS
DEVELOPMENTDEVELOPMENTTOOLSTOOLS
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OBJECTIVESOBJECTIVES
In the end of this section, student should be able to:
Differentiate common system development tools:
(a) modelling
(b) prototyping
(c) CASE tools
List and explain five phases of the SDLC:
(a) planning
(b) analysis
(c) design
(d) implementation
(e) support
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System
Development
Tools
System
Development
Tools
Prototyping
Modelling
CASE tools
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(a) Modelling(a) Modelling
Models are needed in order to help the
analyst to understand the functionality ofthe system and models are used to
communicate with customers.
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Types of modelling:
i) Data processing model data is
processed at different stages
ii) Composition model entities arecomposed of other entities
(a) Modelling (cont.)(a) Modelling (cont.)
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iii)Architectural model showing principal
sub-system
iv) Classification model entities have
common characteristics
v) Stimulus/response model systems
reaction to events
(a) Modelling (cont.)(a) Modelling (cont.)
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(b) Prototyping(b) Prototyping
Prototyping is the process of building amodel of a system.
In terms of an information system,
prototypes are employed to help systemdesigners build an information systemthat intuitive and easy to manipulate forend users.
Prototyping is an iterative process that ispart of the analysis phase of the SDLC
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Advantages of Prototyping:(a) Reduces development time.
(b) Reduces development costs.
(c) Requires user involvement.(d) Developers receive
quantifiable user feedback.
(e) Facilitates system implementation
since users know what to expect.
(f) Results in higher user satisfaction.
(g) Exposes developers to potential
future system enhancements.
(b) Prototyping (cont.)(b) Prototyping (cont.)
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Disadvantages of prototyping:
(a) Can lead to insufficient analysis.
(b) Users expect the performance of the
ultimate system to be the same as the
prototype.
(c) Developers can become too attached
to their prototypes.(d) Can cause systems to be left
unfinished and / or implemented
before they are ready.
(b) Prototyping (cont.)(b) Prototyping (cont.)
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(e) Sometimes leads to incomplete
documentation.
(f) If sophisticated software prototypes(4th GL or CASE Tools) are employed,
the time saving benefit of prototyping
can be lost.
(b) Prototyping (cont.)(b) Prototyping (cont.)
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(c) CASE tools(c) CASE tools
CASE is the abbreviation of Computer-
Aided Software Engineering.
CASE tools are productivity tools for
systems analysts that have been createdexplicitly to improve their routine work
through the use of automated support
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Reasons for using CASE tools
- Increasing Analyst Productivity
- Improving Analyst-User
Communication
- Integrating Life Cycle Activities
- Accurately Assessing Maintenance
Changes
(c) CASE tools (cont.)(c) CASE tools (cont.)
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Case Tool Classifications:
1.Upper CASE tools perform analysis and
design
2. Lower CASE tools generate programs
from CASE design
3. Integrated CASE tools perform both
upper and lower CASE functions
(c) CASE tools (cont.)(c) CASE tools (cont.)
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Upper CASE Tools
- Create and modify the system design
- Help in modeling organizational
requirements and defining system
boundaries
- Can also support prototyping of screen
and report designs
(c) CASE tools (cont.)(c) CASE tools (cont.)
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Lower CASE tools
- Lower CASE tools generate computersource code from the CASE design
- Source code is usually generated in
several languages
-Traditional versus CASE systems
development life cycle
(c) CASE tools (cont.)(c) CASE tools (cont.)
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Analysis DesignProgram
Design &
Coding
Program
Testing
Installation
Requirements
ProgramSpecs
ProgramSourceCode
CompletedSystem
DesignQuestions
ProgramSpecificationQuestions
Program Bugsand Errors
InstallationBugs
Design Upper CASEToolset
Lower CASEToolset(Code
Generation)
Installation
Requirements
CASEDesignEntities
CASERepository
Error-FreeComputerSystem
DesignQuestions
Design Flaws &Inconsistencies
CASE Systems Development Life Cycle
Traditional Systems Development Life Cycle
Analysis
Traditional vs CASE SDLCTraditional vs CASE SDLC
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System Development Tools
Differentiation
System Development Tools
Differentiation
MODELLING PROTOTYPING CASE tools
Abstract
descriptions ofsystem
Process of building
a model of asystem
Software systems
which are intendedto provide
automated support
for softwareprocess activities.
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THE SYSTEMSTHE SYSTEMS
DEVELOPMENTDEVELOPMENT
LIFE CYCLELIFE CYCLE
(SDLC)(SDLC)
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The systems development life cycle is a
phased approach to solving businessproblems
Developed through the use of a specific
cycle of analyst and user activities Each phase has unique user activities
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The systems development life cycle
(SDLC) is a general term used to describethe method and process of developing a
new information system
W
ithout the structure and organizationprovided by SDLC approach projects are
at risk for missed deadline, low quality etc.
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SDLC provides
StructureMethods
Controls
ChecklistNeeded for successful development
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Phases of the SDLCPhases of the SDLC
The SDLC is composed of five fundamental
phases (major phases):
Planning
Analysis
Design
Implementation
Support
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Each of the phases include a set
of steps, which rely on
techniques that produce specific
document files that provide
understanding about the project.
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Phase I : PlanningPhase I : Planning
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This phase is the fundamental process of
understanding why an information system
should be built.
The Planning phase will also determine
how the project team will go about building
the information system.
The Planning phase is composed of two
planning steps.
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Two Planning StepsTwo Planning Steps
1. During project initiation, the
systems business value to the
organization is identified (How will
it lower costs or increaserevenues?)
2. During project management, the
project manager creates a work
plan, staffs the project, and putstechniques in place to help the
project team control and direct the
project through the entire SDLC.
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Phase II : AnalysisPhase II : Analysis
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The analysis phase answers the questions of who
will use the system, what the system will do, and
where and when it will be used.
During this phase the project team investigates
any current systems, identifies improvement
opportunities, and develops a concept for thenew system.
This phase has three analysis steps.
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Phase I : Planning
Three Analysis StepsThree Analysis Steps
1. Analysis strategy: This is developed to guidethe projects teams efforts. This includes an
analysis of the current system.2. Requirements gathering: The analysis of this
information leads to the development of aconcept for a new system. This concept is
used to build a set of analysis models.3. System proposal: The proposal is presentedto the project sponsor and other keyindividuals who decide whether the projectshould continue to move forward.
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The system proposal is the initial deliverable that
describes what business requirements the newsystem should meet.
The deliverable from this phase is both an
analysis and a high-level initial design for thenew system.
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Phase III : DesignPhase III : Design
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Is the process of defining thearchitecture, components,
modules, interfaces and data for
a system to satisfy specifiedrequirements
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Five Design StepsFive Design Steps
1. Design Strategy: This clarifies
whether the system will be developed
by the company or outside the
company.
2. Architecture Design: This describes
the hardware, software, and network
infrastructure that will be used.
3. Interface Design: Define the software
that will be used and how the system
will look alike.
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4. Database and File Specifications:
These documents define what and
where the data will be stored.
5. Program Design: Defines whatprograms need to be written and
what they will do.
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Phase IV: ImplementationPhase IV: Implementation
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Processes and DeliverablesProcesses and Deliverables
During this phase, the system is
either developed or purchased (in
the case of packaged software).
This phase is usually the longest
and most expensive part of the
process.
The phase has three steps.
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1. System Construction: The system
is built and tested to make sure it
performs as designed.
2. Installation: Prepare to support the
installed system.
3. Support Plan: Includes a post-
implementation review.
Three Implementation StepsThree Implementation Steps
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Phase V: SupportPhase V: Support
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Is needed by the customer to
make sure that problems will besolved.
The developer should be giving
training and support accordingto their agreement with the
customer.
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Process Product
Planning
Analysis
Design
Implementation
Project Plan
System Proposal
SystemSpecification
New System andMaintenance Plan
SummarySummary
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