chap 1 - system life cycle
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Objective
To understand various activities involved
in system life cycle and different lifecycle models
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Scope
Activities involved in life cycle model
Different life cycle models
Waterfall Model Prototyping
Object Oriented
Dynamic System Development Model Comparing different models
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Activities in System Life Cycle
Preliminary
Investigation
Analysis
Design
Development/
coding
Testing
Implementation
and maintenance
Start
Stop
If new additions are to be
introduced in the system
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Activities in System Life Cycle
Preliminary Investigation
Identification of problem
Listing down of possible solutions Feasibility Study
Recommendations
Analysis It is the detailed study of various operations
performed by the system
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Activities in System Life Cycle
Design
Structure or design for the proposed system is
finalized.These includes files, databases, inputs,
outputs, and screens.
Development
System is built using design specification
Testing
System is tested for its accuracy
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Activities in System Life Cycle
Implementation and Maintenance
Implementation is putting the system on users
site for operation
Possible changes leading to changes during the
implementation are:
change in the policies of organization or
change in users requirements, For this maintenance is required.
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Life Cycle Models
Waterfall Model
Prototyping
Object oriented Dynamic System Development Method
(DSDM)
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Analysis
Design
System Engg.
Coding
Testing
Maintenance
Waterfall Model
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Prototyping
Steps:
Identify the users information and operatingrequirements.
Based upon these, build a working prototype ofthe proposed system.
Let the customer evaluate the prototype. If thereare changes suggested, incorporate them in the
prototype.
Repeat the process unless the system meets fulluser requirements
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Requirement
gathering
Quick Design
Engineer Product
Building
Prototype
Refining
Prototype
Customer
evaluation
Start
Stop
Prototype Model
Prototyping
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Object Oriented Model
This model uses object oriented techniques
during different system development phases
(e.g. analysis, design, implementation)
Everything is viewed as Objects.
Objects can be any distinguishable thing.
It can be person, place, thing, or someconcept.
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Object Oriented Process
The system to be developed is observed and
analyzed and the requirements are defined as
in any other method of system development.
Then the objects in the required system are
identified.
Relationships between objects are identified
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Object Oriented Process
The basic steps of system designing using
Object Modeling
System Analysis
System Design
Object Design
Implementation
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O O Modeling - System Analysis
Developer interacts with the user of thesystem to find their requirements
Study of the system is also done to understand
the functioning
Analyst prepares a model of the desiredsystem showing its possible objects
This model shows the functionality of thesystem. It doesnt show implementationdetails.
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O O Modeling - System Design
Architecture of the desired system is decided
The system is organized as a set of
subsystems interacting with each other The stress lies on the objects comprising the
system
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O O Modeling - Object Design
The details of the system analysis and system
design are implemented.
The objects identified in the system designphase are designed.
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O O Modeling - Implementation
The class objects and the interrelationships of
these classes are coded using programming
language decided upon.
The databases are made and the complete
system is given a functional shape.
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Basic Object Models
models used by analyst to analyze and depict
objects in a system:
Object Model Dynamic Model
Functional Model
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Basic Object Models
Object Model
describes the objects in a system and their
interrelationships
Observes all the objects as static
Does not pay any attention to their dynamic
nature.
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Basic Object Models
Dynamic Model
depicts the dynamic aspects of the system
Portrays the changes occurring in the states of various
objects with the events that might occur in the system.
Functional Model basically describes the data transformations of the
system
Describes the flow of data and the changes that occur
to the data throughout the system
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DSDM- Dynamic System Development Model
Dynamic approach towards system
development
It is a Rapid Application Developmentmethod
Uses incremental prototyping.
Is independent of tools As it can be used with both structured analysis
and design approach or object-oriented approach.
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DSDM
Is particularly useful in situations where
System is to be developed in short time span
requirements cannot be frozen at the start of the
application building.
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DSDM
DSDM is five phase life cycle
Feasibility
Business Study
Functional Model Iteration
Design and Build Iteration
Implementation
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DSDM - Feasibility Study
Problem is defined
Technical feasibility of the desired
application is verified Applications suitability for Rapid
Application Development (RAD) approach is
checked
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DSDM - Business Study
Overall business study of the desired system
is done
The business requirements and informationrequirements out of the system are identified
The basic architectural framework of the
desired system is prepared
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DSDM-Functional Model Iteration
Prototype for the system is built iteratively
Prototype is improved through
demonstration to the user taking the feedback and
incorporating the changes.
Cycle is repeated generally twice or thriceuntil a part of functional model is agreed upon
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DSDM-Design and Build Iteration
This phase stresses upon ensuring that theprototypes are satisfactorily and properlyengineered to suit their operational
environment Software components designed during the
Functional modeling are further refined till
they achieve a satisfactory standard. The product of this phase is a tested system
ready for implementation.
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DSDM - Implementation
Users are trained
The system is actually put into the operational
environment.
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Agr ee pl an
Functi onal
Model
Iteration
Review Pr ot ot ype
Cr eat e
Func.
Pr ot o.
Identify
func
Prot o
I mple ment
Tr ai n
Users
Review
Busi ness
I mple ment ation
Identify design prot ot ype
Desi gn &
buil d iterati on
Revise
desi gn
prot o
Cr eate design prot ot ype
Agree
pl an
User appr oval &gui deli nes
Feasi bilit y
Busi ness
St udy
DSDM System Life Cycle
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Comparing different models
Waterfall Model
Limitations
Real projects rarely follow sequential flow.
Iterations are always required.
Requirements may not be clearly defined in thebeginning phase.
Customer would have no idea of the workingprogram until the end.
Product delivery takes much time.
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Prototyping
Limitations
Because of quick design, there can be
compromise on quality.
Advantages:
Reduces risk of uncertainty
Allows early stoppage of unsuccessful projects.
User interaction and involvement is more.
Less chances of error during system design.
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DSDM Model
Advantages:
Quality of the product is improved due to
Active user participation throughout the life of the
project
Iterative nature of development
DSDM ensures rapid deliveries
Reduced project costs due to advantagesmentioned above
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Object Oriented Method Advantages
Easier to produce and understand designs as itclosely represents the problem domain
Allows changes more easily as the objects in the
system are immune to requirement changes
Encourages re-use - new applications can use theexisting modules
Reduced development cost and cycle time.
Is more natural
provides nice structure for thinking andabstracting and leads to modular design.
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Summary
The systems development life cycle consists
of following 5 phases:
Analysis
Design
Coding
Testing
Maintenance
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Summary
Various life cycles models are available in the
industry.
Traditional(Waterfall)
Prototype
Object-Oriented
Dynamic systems development method
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Summary
Waterfall Model is a sequential model where
each stage can only start after the previous
stage has finished.
Prototype is an iterative model where
enhancements are made on the prototype of
the system.
Object Oriented Model uses object oriented
techniques during different stages of
development
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Summary
DSDM combines RAD with incremental
model of system development.
Each model has its own limitations and
advantages. These should be taken into
consideration while deciding for a
methodology.
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