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40 lines
2.5 KiB
40 lines
2.5 KiB
# Software development life cycles (SDLC)
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Here are several popular SDLC models:
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## Waterfall
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The waterfall model is best suited for well-defined complex projects, where problems can be spotted early and complexity is dealt with in an orderly way. Key distadvantages include low customer visibility and low flexibility to mid-project changes.
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## Incremental development
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"Incremental" here refers to adding to the work products (requirements, source code, etc.) in stages. In each stage, more functionality is added (core functionality first).
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## Iterative development
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In iterative development one iterates through the whole process (requirements → ... → deployment) multiple times. Iterative and incremental development often go together.
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## Spiral
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Spiral is a type of incremental and iterative development where risk assessment occurs at the start of each cycle.
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## Agile
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Agile is a form of incremental and iterative development with emphasis on frequent face-to-face communication, high customer visibility, adaptability to change, and minimizing non-software work products. For example, Extreme Programming (XP) is an agile methodology based on the principles of communication, simplicity, feedback, courage, and respect.
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## Evolutionary
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In an evolutionary model, deliverables are given to the customer frequently and incrementally. The focus is on high-value features first and getting customer feedback early and often.
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## Code & Fix
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This is a kind of incremental development where life cycle phases other than coding and debugging (requirements analysis, software design, testing, etc.) are skipped, and code refactoring is often neglected.
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## Prototyping
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This isn't really a life cycle on its own (although it can be adapted as such, as with "evolutionary prototyping"). Rather, it's a technique that is good for dealing with unclear requirements, assisting in communication, or in developing initial user interface design.
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# Questions guiding the choice of SDLC model
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This list is adapted from *Rapid Development* by Steve McConnell.
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- How well do the customer and development team understand the requirements?
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- How likely are requirements to change?
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- Are major archiectural changes likely?
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- Are there hard schedule constraints?
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- Are the relevant tools and technologies well-understood by the development team?
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- Is high visibility important to customers and/or management?
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- How will human factors affect the project (discipline, skills, training, and intellectual limits)?
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- What opportunities are there to parallelize work phases?
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