4 Emergent approaches to software development

Iterative and incremental methods have been widely adopted in software development. Nowadays, high competitiveness, reduced time-to-market and pressure to develop flexible enterprise software together with the rapid change of technology have led to the emergence of new approaches to building, deploying and maintaining software. At the time of writing (2005), several new approaches to software development have been established that may become significant during the lifetime of this course. These include Model Driven Architecture (MDA) (see http://www.omg.org/mda/) and agile development (see http://agilemanifesto.org/).

MDA defines an approach whereby business-oriented decisions and specifications can be separated from implementation and platform (technology) decisions. The idea is to distinguish between platform independent models (PIMs) specified using UML, and platform specific models (PSMs) which carry relevant information for the generation of platform-specific code. Standard mappings between PIMs and PSMs should allow tools to be developed to automate some of the implementation. This approach is based on strong emphasis on:

• models specified in a well-defined notation;

• transformations between models;

• formal underpinning of models and transformations;

• industry adopted standards and tools.

Agile development (Cockburn and Highsmith, 2001; Fowler and Highsmith, 2001) is an umbrella term used to describe a variety of (agile) methods that encourage continual realignment of development goals with the needs and expectations of the customer. It represents a compromise between no process and too much process; a lighter weight, faster and nimbler software development process that can adapt to the inevitable changes in customer requirements.

The Agile Manifesto lists the following four principles:

Extreme Programming (XP) (Beck, 2000) is one of the best known agile methods; it is very lightweight method, based on intensive testing and incremental development. It defines a series of practices such as small releases, simple design, testing, programming in pairs, collective ownership, continuous integration, 40-hour week, on-site customer, and coding standards.