SDLC Models Advantages and Disadvantages

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Software development methodologies

• Presented by
• Farida anwar
• Bsit-7th morning
• Subject itproject management
• University of okara

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Methodologies

• Waterfall
• Prototype model
• Incremental
• Iterative
• V-Model
• Spiral
• Scrum
• Cleanroom
• RAD

• DSDM
• RUP
• XP
• Agile
• Lean
• Dual Vee Model
• TDD
• FDD

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Waterfall

• Sequential design process
• Progress is seen as flowing steadily downwards
  (like a waterfall) through SDLC

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Advantages and of the Waterfall Model

• Suitable for simple or smaller projects
• Requirements are well understood
• Easy to understand
• Easy to manage
• Clear milestones
• Disadvantages
• High amounts of risk and uncertainty.
• Not a good model for complex and
  object-oriented projects.
• Poor model for long and ongoing projects.
• Does not allow scope changes
• Does not allow for requirement changes
• Unable to easily handle unexpected risks

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Prototyping

• Creating prototypes of software applications i.e.
  Incomplete versions of the software program being
  developed
• A prototype typically simulates only a few
  aspects of, and may be completely different from,
  the final product.

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Advantages of Prototype model

• Users are actively involved in the development
• Reduced time and costs
• Improved and increased user involvement
• Errors can be detected much earlier.
• Quicker user feedback is available leading to
  better solutions.
• Disadvantages
• Incomplete application may cause application not
  to be used as the full system was designed
  incomplete or inadequate problem analysis.
• Leads to implementing and then repairing way of
  building systems.
• Expense of implementing prototyping
• Prototyping is usually done at the cost of the
  developer
• It is a slow process.

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Incremental Build Model

• The model is designed, implemented and tested
  incrementally (a little more is added each time).
• Finished when satisfies all the requirements.
• Combines the elements of the waterfall model with
  the iterative philosophy of prototyping.

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Advantages of Incremental model

• Generates working software quickly and early
  during the software life cycle.
• This model is more flexible less costly to
  change scope and requirements.
• It is easier to test and debug during a smaller
  iteration.
• In this model customer can respond to each built.
• Lowers initial delivery cost.
• Easier to manage risk because risky pieces are
  identified and handled during itd iteration.
• Disadvantages
• Needs good planning and design.
• Needs a clear and complete definition of the
  whole system before it can be broken down and
  built incrementally.
• Total cost is higher than waterfall.

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Iterative and Incremental Development

• Iterative and incremental development is any
  combination of both iterative design or iterative
  method and incremental build model for
  development.

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Incremental vs. Iterative
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A Bit Different Understanding
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Effort in Iterative Development
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Spiral Model

• Combining elements of design and
  prototyping-in-stages
• Combines the features of the prototyping and the
  waterfall model
• The spiral model is intended for large, expensive
  and complicated projects
• Advantages of top-down and bottom-up concepts

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Advantages of Spiral model

• High amount of risk analysis hence, avoidance of
  Risk is enhanced
• Good for large and mission-critical projects.
• Strong approval and documentation control.
• Additional Functionality can be added at a later
  date.
• Software is produced early in the software life
  cycle.
• There is always a space for customer feedback. 
• Disadvantages of Spiral model
• Can be a costly model to use.
• Risk analysis requires highly specific expertise.
• Doesnt work well for smaller projects.
• For its smooth operation spiral model protocol
  needs to be followed strictly
• It is not suitable for low risk projects.

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Background

• Top-down
• deductive reasoning
• analysis or decomposition
• Descartes
• G gt 1

• Bottom-up
• inductive reasoning
• synthesis
• Bacon
• 1 gt G

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RAD

• Minimal planning and fast prototyping.
• Developing instead of planning
• The lack of pre-planning generally allows
  software to be written much faster, and makes it
  easier to change requirements.

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Advantages of the RAD model
Reduced development time. Flexible and
adaptable to changes Increases reusability of
components Quick initial reviews
occur Encourages customer feedback With less
people, productivity can be increased in short
time Each phase in RAD delivers highest
priority functionality to client Disadvantages of
RAD model Requires highly skilled
developers/designers. It can't be used for
smaller projects When technical risk is high,
it is not suitable Not all application is
compatible with RAD High dependency on modeling
skills
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Cleanroom

• The cleanroom process embeds software development
  and testing within a statistical quality control
  framework.
• Mathematically-based software development
  processes are employed to create software that is
  correct by design, and statistical usage testing
  processes are employed to provide inferences
  about software reliability.

• This systematic process of assessing and
  controlling software quality during development
  permits certification of software fitness for use
  at delivery.

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Agile

• Group of software development methods
• Based on iterative and incremental development
• Most important phrases
• Self-organizing, cross-functional teams
• Adaptive planning,
• Evolutionary development and delivery,
• A time-boxed iterative approach,
• Rapid and flexible response to change.
• A conceptual framework
• The agile manifesto in 2001.

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Advantages of Agile

• Agile methodology has an adaptive approach which
  is able to respond to the changing requirements
  of the clients
• Direct communication and constant feedback from
  customer representative leave no space for any
  guesswork in the system
• Disadvantages
• This methodology focuses on working software
  rather than documentation, hence it may result in
  a lack of documentation
• The software development project can get

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Scrum

• Scrum is an iterative and incremental agile
  software development framework
• A flexible, holistic product development strategy
• Development team works as an atomic unit
• Opposing to sequential approach

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Advantages of Scrum

• Saves time as well as money as regular sprint
  is held to review the task.
• Involves the customer and stakeholders at each
  phase.
• It also works best for all fast-moving product
  developments.
• Scrum takes feedback from product owner and
  stakeholders.
• The individual effort of each and every team
  member is transparent and appreciated.
• Disadvantages of Scrum
• The framework can be successful only with
  experienced team members.
• This methodology works best with small teams
  than a large team of developers.
• Adopting this methodology for a large team can be
  challenging.
• The project is likely to suffer if any of the
  members leaves the project in the middle.

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Lean (Kanban)

• A translation of lean manufacturing principles
  and practices
• Toyota production system,
• Today part of agile community.

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Lean Principles

• Eliminate waste
• Amplify learning
• Decide as late as possible
• Deliver as fast as possible
• Empower the team
• Build integrity in
• See the whole

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Extreme Programming (XP)

• Improve software quality and responsiveness to
  changing customer requirements
• A type of agile software development
• Frequent "releases" in short development cycles
• Introduce checkpoints where new customer
  requirements can be adopted.

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XP Concepts (examples only)

• Pair programming
• Planning game
• Test-driven development
• Continuous integration

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Advantages

• Extreme programming methodologies emphasis on
  customer involvement.
• This model helps to establish rational plans and
  schedules and to get the developers personally
  committed to their schedules which are surely a
  big advantage in the XP model.
• This model is consistent with most modern
  development methods so, developers are able to
  produce quality software.
• save costs and time required for project
  realization.
• Disadvantages
• This methodology is only as effective as the
  people involved, Agile does not solve this issue.
• This kind of software development model requires
  meetings at frequent intervals at enormous
  expense to customers.
• It requires too much development changes which
  are really very difficult to adopt every time for
  the software developer.
• In this methodology, it tends to impossible to be
  known exact estimates of work effort needed to
  provide a quote, because at the starting of the
  project nobody aware about the entire scope and
  requirements of the project.

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DSDM

• An agile project delivery framework, primarily
• DSDM fixes cost, quality and time at the outset
  and uses the Moscow prioritization of scope
• Pareto principle

• M - MUST describes a requirement that must be
  satisfied in the final solution for the solution
  to be considered a success.
• S - should represents a high-priority item that
  should be included in the solution if it is
  possible. This is often a critical requirement
  but one which can be satisfied in other ways if
  strictly necessary.
• C - could describes a requirement which is
  considered desirable but not necessary. This will
  be included if time and resources permit.
• W - would represents a requirement that
  stakeholders have agreed will not be implemented
  in a given release, but may be considered for the
  future.

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Advantages of DSDM

• Users are highly involved in the development of
  the system so, they are more likely to get a grip
  on the software development project.
• In this model, basic functionality is delivered
  quickly, with more functionality being delivered
  at frequent intervals.
• This method provides an easy access by developers
  to end-users.
• In this kind of development, approach projects
  are delivered on time and within a specific
  budget.
• Disadvantages
• The first thing is DSDM is costly to implement,
  as it requires users and developers both to be
  trained to employ it effectively. It may not be
  suitable for small organizations or one-time
  projects
• It is a relatively new model, therefore, it is
  not very common to understand.

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Test-driven development (TDD)

• Relies on the repetition of a very short
  development cycle first the developer writes an
  (initially failing) automated test case that
  defines a desired improvement or new function,
  then produces the minimum amount of code to pass
  that test, and finally refactors the new code to
  acceptable standards.

• Test-first programming concept of extreme
  programming in the beginning
• Today standalone methodology

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TDD ADVANTAGES

• .Writing tests first require you to really
  consider what you want from the code
• Short feedback loop
• Creates a detailed specification
• Reduced time in rework
• Less time spent in the debugger and when it is
  required you usually get closer to problem
  quickly.

• TDD Disadvantages
• It takes a lot of time and effort which creates a
  sense of slow development.
• TDD focuses on simplest design for current sprint
  and doesnt tackle for future major refactoring.
• Its hard to test the interface because of
  continuous changes.
• THINGS TO AVOID WHILE WRITING TEST CASES

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Rational Unified Process (RUP)

• An iterative software development process
  framework created by the rational software
  corporation (IBM)
• Not a concrete prescriptive process, but an
  adaptable framework, intended to be tailored by
  the development organizations
• Expected to select elements of the process that
  are appropriate

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Advantages of RUP MODEL

• Get high risk and high value first.
• Constant user feedback and engagement.
• Early cohesive core architecture.
• Test early, often, and realistically.
• Apply use cases where needed.
• Do some visual modeling with UML.
• Manage requirements.
• Manage change requests and configuration.
• Disadvantages of RUP
• RUP is not considered particularly agile
  However, recent studies have shown that by
  adopting the right essential artifacts RUP is
  agile.
• It fails to provide any clear implementation
  guidelines.
• RUP leaves the tailoring to the user entirely.

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Feature-driven development (FDD)

• Iterative and incremental development process.
• An agile method
• Driven from a client-valued functionality
  (feature) perspective
• Mostly part of other methodologies

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Advantages of FDD Methodology

• FDD Helps to move larger size projects and obtain
  repeatable success.
• The simple five processes help to bring work done
  in a short time and easiest manner.
• This type of model is built on set standards for
  software development industry, so it helps easy
  development and industry recognized best
  practices.
• Disadvantages
• Not an ideal methodology for smaller projects so,
  it is not good for an individual software
  developer.
• High dependency on the main developer means the
  person should be fully equipped for an act as
  coordinator, lead designer, and mentor.
• No written documentation provided to clients in
  this methodology so, they are not able to get a
  proof for their own software.

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V-model

• The v-model is an extension of the waterfall
  model.
• Show the relationships between development phases
  and test phases
• Time and project completeness vs. Level of
  abstraction

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Advantages of V-model

• Easy to use
• Simple to use
• Time saving, quick
• Works well for small projects where
  requirements are easily understood
• Covers all functional areas.
• Disadvantages of V-Model
• Very rigid
• Least flexible
• Software is developed during the implementation
  phase, so no early prototypes of the software are
  produced
• Risky

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Dual Vee Model

• Describes a model of complex development
• For example
• Hardware
• Platform
• Application software
• Development of a system's architecture is the
  big V
• Components/entities developments are the small
  v-s
• It shows interactions and sequences of developing
  a complex system and a system of systems.

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Shouldnt forget
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Waterfall

• Details

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Waterfall 1

• Jump to next phase only if the prior one is
  completed
• Pros
• Detailed early analysis cause huge advantages at
  later phases
• If a bug found earlier, it is much cheaper (and
  more effective) to fix than bugs found in a later
  phase
• Requirement should be set before design starts
• Points to importance of documentation (minimized
  broken leg issue)
• Disciplined and well-structured approach
• Effective for stable software projects
• Easy to plan from project management point of view

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Waterfall 2

• CONs
• Changes are expensive
• Client does not explicitly know what he or she
  wants
• Client does not explicitly know what is possible
  to have
• Need to finish every phase fully
• Long projects, difficult to keep the plan
• Designers may not know in advance how complex a
  features implementation
• Measure twice, cut once

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• Questions????