The document discusses agile development models as an alternative to traditional waterfall models. Some key points: - Agile models were proposed in the 1990s to address issues with waterfall models like cost overruns and inability to adapt to changes. - Agile follows an incremental and iterative approach where requirements are broken into small parts developed over iterations of a few weeks each. Working software is delivered after each iteration. - Core principles of agile include frequent delivery of working software, ability to incorporate requirement changes efficiently, and continuous customer interaction/feedback.

1. AGILE DEVELOPMENT MODELS
 Difficulties of waterfall-based development
Model
 1. Cost escalation in waterfall-based development
projects. (Modification after SRS – By nature
modification will happen).
 2. Customised application development is not
possible.
 3. Waterfall model is called a heavy weight model.
 4. Waterfall model prescribes almost no customer
interactions after the requirements have been
specified

2.  The agile software development model was proposed in the
mid-1990s to overcome the shortcomings of the
waterfall model of development identified above.
 To adapt to change requests quickly.
 A few popular agile SDLC models are the following:
 Crystal
 Atern (formerly DSDM)
 Feature-driven development
 Scrum
 Extreme programming (XP)
 Lean development
 Unified process

3.  The requirements are decomposed into many small
parts that can be incrementally developed.
 The agile models adopt an incremental and iterative
approach.
 Each incremental part is developed over an iteration.
 Each iteration is intended to be small and easily
manageable and lasts for a couple of weeks only.
 At a time, only one increment is planned, developed,
and then deployed at the customer site.

4.  The time to complete an iteration is called a time box.
 A central principle of the agile model is the delivery of
an increment to the customer after each time box.

5. 1. Essential Idea behind Agile Models
 The agile model emphasises incremental release of
working software as the primary measure of
progress.
 Each agile project usually includes a customer
representative in the team.
 At the end of each iteration, stakeholders and the
customer representative review the progress made
and re-evaluate the requirements.
 The developed increment is installed at the
customer site.

6.  Agile models emphasise use of face-to-face
communication - the development team size be kept
small (5-9 people) - collaborative work environment.
 It is implicit that the agile model is suited to the
development of small projects.

7. Principles behind the agile model
 1. Working software over comprehensive
documentation.
 2. Frequent delivery of incremental versions of the
software to the customer in intervals of few weeks.
 3. Requirement change requests from the customer
are encouraged and are to be efficiently incorporated.
 4. Face-to-face communication
 5. Continuous interaction with the customer
 6. Agile development projects usually deploy pair
programming.

8. Advantages and disadvantages of agile methods
 Advantages:
 It overcomes major drawbacks.
 Disadvantages:
 Lack of formal documents.
 It is difficult to get important project decisions due to
lack of documents.
 When a project completes and the developers disperse,
maintenance can become a problem.

9. Agile versus Other Models
 Agile model versus iterative waterfall model
Agile Model Iterative Model
Progress is measured in
terms of the developed and delivered
functionalities.
Progress is generally measured in
terms of the number of completed
and reviewed artifacts
frequent delivery of
working versions of the software is
made
Not like that
The client get some code even if the
project is cancelled in middle
No code is delivered if so.

10. Agile versus exploratory
programming
Agile Exploratory
frequent re-evaluation of plans Not like that
face-to-face communication Not like that

11. Agile model versus RAD model
Agile model RAD model
does not recommend developing
prototypes
design quick-and-dirty prototypes
Agile projects logically break down the
solution into features that are
incrementally
developed and delivered.
The RAD approach does not
recommend this.
Agile teams only demonstrate
completed work to the customer.
RAD
teams demonstrate to customers screen
mock ups, and prototypes