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Home > Browse Topics > Development
QuickStudy: System Development Life Cyc
Quickstudy by Russell Kay
DEFINITION: Definition
System Development Life
Cycle (SDLC) is the overall
process of developing
information systems through
a multistep process from
investigation of initial
requirements through
analysis, design,
implementation and
maintenance. There are
many different models and
methodologies, but each
generally consists of a series
of defined steps or stages.
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MAY 14, 2002
(COMPUTERWORLD) - Once
upon a time, software
development consisted of a
programmer writing code to solve a problem or automate a procedur
systems are so big and complex that teams of architects, analysts, p
testers and users must work together to create the millions of lines o
code that drive our enterprises.
To manage this, a number of system development life cycle (SDLC)
been created: waterfall, fountain, spiral, build and fix, rapid prototypin
http://www.computerworld.com/developmenttopics/development/story/0,10801,71151,00.... 7/30/2005
System Development Life Cycle - Computerworld
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and synchronize and stabilize.
The oldest of these, and the best known, is the waterfall: a sequence
which the output of each stage becomes the input for the next. These
characterized and divided up in different ways, including the following
z
z
z
z
z
z
z
Project planning, feasibility study: Establishes a high-level v
intended project and determines its goals.
Systems analysis, requirements definition: Refines project g
defined functions and operation of the intended application. An
information needs.
Systems design: Describes desired features and operations in
including screen layouts, business rules, process diagrams, ps
other documentation.
Implementation: The real code is written here.
Integration and testing: Brings all the pieces together into a s
environment, then checks for errors, bugs and interoperability.
Acceptance, installation, deployment: The final stage of initi
where the software is put into production and runs actual busin
Maintenance: What happens during the rest of the software's
correction, additions, moves to a different computing platform a
the least glamorous and perhaps most important step of all, go
forever.
But It Doesn't Work!
The waterfall model is well understood, but it's not as useful as it onc
1991 Information Center Quarterly article, Larry Runge says that SD
well when we are automating the activities of clerks and accountants
nearly as well, if at all, when building systems for knowledge workers
help desks, experts trying to solve problems, or executives trying to l
company into the Fortune 100."
Another problem is that the waterfall model assumes that the only ro
specifying requirements, and that all requirements can be specified i
Unfortunately, requirements grow and change throughout the proces
calling for considerable feedback and iterative consultation. Thus ma
models have been developed.
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System Development Life Cycle - Computerworld
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The fountain model recognizes that although some activities can't sta
-- such as you need a design before you can start coding -- there's a
overlap of activities throughout the development cycle.
The spiral model emphasizes the need to go back and reiterate earli
number of times as the project progresses. It's actually a series of sh
cycles, each producing an early prototype representing a part of the
This approach helps demonstrate a proof of concept early in the cyc
accurately reflects the disorderly, even chaotic evolution of technolog
Build and fix is the crudest of the methods. Write some code, then ke
until the customer is happy. Without planning, this is very open-ende
risky.
In the rapid prototyping (sometimes called rapid application developm
initial emphasis is on creating a prototype that looks and acts like the
product in order to test its usefulness. The prototype is an essential p
requirements determination phase, and may be created using tools d
those used for the final product. Once the prototype is approved, it is
the "real" software is written.
The incremental model divides the product into builds, where section
are created and tested separately. This approach will likely find error
requirements quickly, since user feedback is solicited for each stage
code is tested sooner after it's written.
Big Time, Real Time
The synchronize and stabilize method combines the advantages of t
with technology for overseeing and managing source code. This met
many teams to work efficiently in parallel. This approach was defined
of Harvard University and Michael Cusumano of MIT. They studied h
Corp. developed Internet Explorer and Netscape Communications C
Communicator, finding common threads in the ways the two compan
example, both companies did a nightly compilation (called a build) of
project, bringing together all the current components. They establish
dates and expended considerable effort to stabilize the code before
The companies did an alpha release for internal testing; one or more
(usually feature-complete) for wider testing outside the company, and
release candidate leading to a gold master, which was released to m
some point before each release, specifications would be frozen and
time spent on fixing bugs.
Both Microsoft and Netscape managed millions of lines of code as sp
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System Development Life Cycle - Computerworld
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changed and evolved over time. Design reviews and strategy sessio
frequent, and everything was documented. Both companies built con
into their schedules, and when release deadlines got close, both cho
product features rather than let milestone dates slip.
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