Process Models

Interactive and Incremental Development


P 47 


  • The incremental approach to development allows to reduce them in the development process and gives customers some opportunities to delay decisions on their details requirements until they have some experience with the system.
  • In incremental development, process customers identify in outline the services to be provided by the system.
  • They identify which of the services are the most important and which are least important to them.
  • A number of delivery increments are then defined with each increment providing a subset of the system functionality.
  • The allocation of services to increments are then defined with each increment depends on the service priority.
  • The highest priority services are delivered first to the customers.
  • The system increments have been identified as the requirements for the services to be delivered in the first instruments are defined in detail and developed the most appropriate development process. 
  • During the development of further requirements analysis, for later increment can take place, but charges for the current increment cannot be accessed.
  • Once an increment is completed and delivered, part of the system will be functional, then the new increments are completed. They are integrated with existing increment so the system functionality improves with each delivered increment.



Evolutionary Prototyping



Evolutionary prototyping is based on the idea of developing an initial implementation, exposing to user comments and refining this through many stages until an adequate system has been developed.


This approach to development was used initially for those systems which are difficult or impossible to specify, but now it has become one of the main techniques of development.



Unified Process

The Unified Process or UP is so popular interactive and incremental software development process framework. The most well known and extensively documented refinement of the Unified Process is the Rational Unified Process or RUP.


The Unified Process is not simply a  process, but rather an extensible framework which can and should be customized for specific organizations and/or projects. The Rational Unified Process is,  similarly, a customizable framework. As a result, it is often impossible to say whether refinement of the process was derived from UP or from RUP, and so the names tend to be used interchangeably.


The name Unified Process (as opposed to Rational Unified Process) is generally used to describe the generic process, including those elements which are common to most refinements. The UP name is also used to avoid potential issues of copyright infringement since  Rational Unified Process and RUP is a trademark of IBM.




Iterative and Incremental

The Unified Process is an iterative and incremental development process. The Elaboration, Construction, and Transmission phases are divided into a series of time-boxed iterations. (the Inception phase may also be divided into iterations for a large project). each iteration results in an increment which is a release of the system that contains added or improved the functionality compared with the previous release.


Although most iterations will include work in most of the process disciplines(e,g.Requirements, Design, Implementation, Testing) the relative effort and emphasis will change over the course of the project.



Use Case Driven 

In the Unified Process, use cases are used to capture the functional requirements and to define the contents of the iterations. Each iteration takes a set of Use cases of scenarios from requirements all the way through implementation, test, and deployment.




The Unified Process insists the architecture sit at the heart of the project team’s efforts to shape the system. Since no signal model sufficient to cover all aspects of the system, the  Unified Process supports multiple architectural models and views.


One of the most important deliverables of the process is the executable architecture baseline Which is created during the elaboration phase. This partial implementation of the system serves to validate the architecture and act as a foundation for remaining development.




The Unified Process requires the project team to focus on existing the most critical risks early in the project life cycle. The deliverables of each iteration, especially in the Elaboration phase, must be selected in order to ensure that the greatest risks addressed first.



Project Lifecycle

Profile of a typical project showing the relative sizes of the four phases. The Unified Process divides the project into four phases:

  1. Inception
  2. Elaboration
  3. Construction
  4. Transition




Inception Phase

Inception is the smallest phase in the project, and ideally, it should be quite short. If the Inception Phase is long then it is usually an indication of excessive up-front is a specification, which is contrary to the spirit of the Unified Process.


The following are typical goals for the Inception phase.

  1. Establish a justification for the business case for the project.
  2. Establish the project scope and boundary conditions.
  3. Outline the use cases and key requirements that will drive the design tradeoffs.
  4. Identify risks.
  5. prepare a  primary project schedule and cost estimate.


The Lifecycle objective milestone marks the end of the Inception phase.



Elaboration Phase 

During the Elaboration phase, the project team is expected to capture a healthy majority of the system requirements. However,  the primary goal of Elaboration is to address known risk factors and to establish and validate the system architecture.


The architecture is validated primarily through the implementation of an Executable Architecture Baseline. Discuss the partial implementation of the system which includes the core, most architecturally significant, components. It is built in a series of small, the boxed interactions. By the end of the Elaboration phase, the system architecture must have stabilized and the executable architecture baseline must demonstrate that the architecture will support the key system functionality and exhibit the right behavior in terms of performance, scalability, and cost.


The final celebration phase deliverable in the plan ( including cost and schedule estimates) for the Construction phase. At this point the plan should be accurate and credible since it should be based on the Elaboration phase experience and since significant risk factors should have been addressed during the Elaboration phase.


The Lifecycle architecture milestone marks the end of the Elaboration phase.



Construction Phase

Construction is the largest phase of the project. In this phase, the remainder of the system is built on the foundation laid in Elaboration. System features are implemented in the series of short, time-boxed iterations. Each iteration results in the executable release of the software.


The Initial Operational Capability Milestones marks the end of the Construction phase. 



Transition phase 

The final project phase is the transition. In this phase, the system is deployed to the target users. Feedback received from an initial release (or initial releases) may result in further refinements to be incorporated over the course of the several Transitions phase iterations. The Transition phase also includes system conversions and user training.


The Product Release Milestone marks the end of the Transition phase.

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