Editing Software prototyping (section)

===Evolutionary rapid development===
[[Evolutionary Rapid Development]] (ERD)<ref>Adapted from Software Productivity Consortium. PPS 10–13.</ref> was developed by the Software Productivity Consortium, a technology development and integration agent for the Information Technology Office of the [[Defense Advanced Research Projects Agency]] (DARPA).

:Fundamental to ERD is the concept of composing software systems based on the reuse of components, the use of software templates and on an architectural template. Continuous evolution of system capabilities in rapid response to changing user needs and technology is highlighted by the evolvable architecture, representing a class of solutions. The process focuses on the use of small artisan-based teams integrating software and systems engineering disciplines working multiple, often parallel short-duration timeboxes with frequent customer interaction.

:Key to the success of the ERD-based projects is parallel exploratory analysis and development of features, infrastructures, and components with and adoption of leading edge technologies enabling the quick reaction to changes in technologies, the marketplace, or customer requirements.<ref name=SoftwareProductivityConsortium1997p6/>

To elicit customer/user input, frequent scheduled and ad hoc/impromptu meetings with the stakeholders are held. Demonstrations of system capabilities are held to solicit feedback before design/implementation decisions are solidified. Frequent releases (e.g., [[Development stage#Beta|betas]]) are made available for use to provide insight into how the system could better support user and customer needs. This assures that the system evolves to satisfy existing user needs.

The design framework for the system is based on using existing published or de facto standards. The system is organized to allow for evolving a set of capabilities that includes considerations for performance, capacities, and functionality. The architecture is defined in terms of abstract interfaces that encapsulate the services and their implementation (e.g., COTS applications). The architecture serves as a template to be used for guiding development of more than a single instance of the system. It allows for multiple application components to be used to implement the services. A core set of functionality not likely to change is also identified and established.

The ERD process is structured to use demonstrated functionality rather than paper products as a way for [[Project stakeholder|stakeholders]] to communicate their needs and expectations. Central to this goal of rapid delivery is the use of the "[[timeboxing|timebox]]" method. Timeboxes are fixed periods of time in which specific tasks (e.g., developing a set of functionality) must be performed. Rather than allowing time to expand to satisfy some vague set of goals, the time is fixed (both in terms of calendar weeks and person-hours) and a set of goals is defined that realistically can be achieved within these constraints.  To keep development from degenerating into a "[[random walk]]," long-range plans are defined to guide the iterations. These plans provide a vision for the overall system and set boundaries (e.g., constraints) for the project. Each iteration within the process is conducted in the context of these long-range plans.

Once an architecture is established, software is integrated and tested on a daily basis. This allows the team to assess progress objectively and identify potential problems quickly. Since small amounts of the system are integrated at one time, diagnosing and removing the defect is rapid. User demonstrations can be held at short notice since the system is generally ready to exercise at all times.