Introduction to Software Engineering/Process/Rapid Application Development
Rapid application development (RAD) refers to a type of software development methodology that uses minimal planning in favor of rapid prototyping. The "planning" of software developed using RAD is interleaved with writing the software itself. The lack of extensive pre-planning generally allows software to be written much faster, and makes it easier to change requirements.
Rapid application development is a software development methodology that involves methods like iterative development and software prototyping. According to Whitten (2004), it is a merger of various structured techniques, especially data-driven Information Engineering, with prototyping techniques to accelerate software systems development.
In rapid application development, structured techniques and prototyping are especially used to define users' requirements and to design the final system. The development process starts with the development of preliminary data models and business process models using structured techniques. In the next stage, requirements are verified using prototyping, eventually to refine the data and process models. These stages are repeated iteratively; further development results in "a combined business requirements and technical design statement to be used for constructing new systems".
RAD approaches may entail compromises in functionality and performance in exchange for enabling faster development and facilitating application maintenance.
Rapid application development is a term originally used to describe a software development process introduced by James Martin in 1991. Martin's methodology involves iterative development and the construction of prototypes. More recently, the term and its acronym have come to be used in a broader, general sense that encompasses a variety of methods aimed at speeding application development, such as the use of software frameworks of varied types, such as web application frameworks.
Rapid application development was a response to non-agile processes developed in the 1970s and 1980s, such as the Structured Systems Analysis and Design Method and other Waterfall models. One problem with previous methodologies was that applications took so long to build that requirements had changed before the system was complete, resulting in inadequate or even unusable systems. Another problem was the assumption that a methodical requirements analysis phase alone would identify all the critical requirements. Ample evidence attests to the fact that this is seldom the case, even for projects with highly experienced professionals at all levels.
Starting with the ideas of Brian Gallagher, Alex Balchin, Barry Boehm and Scott Shultz, James Martin developed the rapid application development approach during the 1980s at IBM and finally formalized it by publishing a book in 1991, Rapid Application Development.
Relative effectiveness 
The shift from traditional session-based client/server development to open sessionless and collaborative development like Web 2.0 has increased the need for faster iterations through the phases of the SDLC. This, coupled with the growing use of open source frameworks and products in core commercial development, has, for many developers, rekindled interest in finding a silver bullet RAD methodology.
Although most RAD methodologies foster software re-use, small team structure and distributed system development, most RAD practitioners recognize that, ultimately, no one “rapid” methodology can provide an order of magnitude improvement over any other development methodology.
All types of RAD have the potential for providing a good framework for faster product development with improved software quality, but successful implementation and benefits often hinge on project type, schedule, software release cycle and corporate culture. It may also be of interest that some of the largest software vendors such as Microsoft and IBM do not extensively use RAD in the development of their flagship products and for the most part, they still primarily rely on traditional waterfall methodologies with some degree of spiraling.
This table contains a high-level summary of some of the major types of RAD and their relative strengths and weaknesses.
|Agile software development (Agile)|
|Pros||Minimizes feature creep by developing in short intervals resulting in miniature software projects and releasing the product in mini-increments.|
|Cons||Short iteration may add too little functionality, leading to significant delays in final iterations. Since Agile emphasizes real-time communication (preferably face-to-face), using it is problematic for large multi-team distributed system development. Agile methods produce very little written documentation and require a significant amount of post-project documentation.|
|Extreme Programming (XP)|
|Pros||Lowers the cost of changes through quick spirals of new requirements. Most design activity occurs incrementally and on the fly.|
|Cons||Programmers must work in pairs, which is difficult for some people. No up-front “detailed design” occurs, which can result in more redesign effort in the long term. The business champion attached to the project full time can potentially become a single point of failure for the project and a major source of stress for a team.|
|Joint application design (JAD)|
|Pros||Captures the voice of the customer by involving them in the design and development of the application through a series of collaborative workshops called JAD sessions.|
|Cons||The client may create an unrealistic product vision and request extensive gold-plating, leading a team to over- or under-develop functionality.|
|Lean software development (LD)|
Creates minimalist solutions (i.e., needs determine technology) and delivers less functionality earlier; per the policy that 80% today is better than 100% tomorrow.
|Cons||Product may lose its competitive edge because of insufficient core functionality and may exhibit poor overall quality.|
|Rapid application development (RAD)|
|Pros||Promotes strong collaborative atmosphere and dynamic gathering of requirements. Business owner actively participates in prototyping, writing test cases and performing unit testing.|
|Cons||Dependence on strong cohesive teams and individual commitment to the project. Decision making relies on the feature functionality team and a communal decision-making process with lesser degree of centralized PM and engineering authority.|
|Pros||Improved productivity in teams previously paralyzed by heavy “process”, ability to prioritize work, use of backlog for completing items in a series of short iterations or sprints, daily measured progress and communications.|
|Cons||Reliance on facilitation by a master who may lack the political skills to remove impediments and deliver the sprint goal. Due to relying on self-organizing teams and rejecting traditional centralized "process control", internal power struggles can paralyze a team.|
Since rapid application development is an iterative and incremental process, it can lead to a succession of prototypes that never culminate in a satisfactory production application. Such failures may be avoided if the application development tools are robust, flexible, and put to proper use. This is addressed in methods such as the 2080 Development method or other post-agile variants.
Practical implications 
When organizations adopt rapid development methodologies, care must be taken to avoid role and responsibility confusion and communication breakdown within a development team, and between team and client. In addition, especially in cases where the client is absent or not able to participate with authority in the development process, the system analyst should be endowed with this authority on behalf of the client to ensure appropriate prioritisation of non-functional requirements. Furthermore, no increment of the system should be developed without a thorough and formally documented design phase.
- Whitten, Jeffrey L.; Lonnie D. Bentley, Kevin C. Dittman. (2004). Systems Analysis and Design Methods. 6th edition. ISBN 025619906X.
- Maurer and S. Martel. (2002). "Extreme Programming: Rapid Development for Web-Based Applications". IEEE Internet Computing, 6(1) pp 86-91 January/February 2002.
- Andrew Begel, Nachiappan Nagappan. "Usage and Perceptions of Agile Software Development in an Industrial Context: An Exploratory Study, Microsoft Research". http://research.microsoft.com/pubs/56015/AgileDevatMS-ESEM07.pdf. Retrieved 2008-11-15.
- E. M. Maximilien and L. Williams. (2003). "Assessing Test-driven Development at IBM". Proceedings of International Conference of Software Engineering, Portland, OR, pp. 564-569, 2003.
- M. Stephens, Rosenberg, D. (2003). "Extreme Programming Refactored: The Case Against XP". Apress, 2003.
- Gerber, Aurona; Van der Merwe, Alta; Alberts, Ronell; (2007), Implications of Rapid Development Methodologies, CSITEd 2007, Mauritius, November 2007 
Further reading 
- Steve McConnell (1996). Rapid Development: Taming Wild Software Schedules, Microsoft Press Books, ISBN 978-1556159008
- Kerr, James M.; Hunter, Richard (1993). Inside RAD: How to Build a Fully-Functional System in 90 Days or Less. McGraw-Hill. ISBN 0070342237.
- Ellen Gottesdiener (1995). "RAD Realities: Beyond the Hype to How RAD Really Works" Application Development Trends
- Ken Schwaber (1996). Agile Project Management with Scrum, Microsoft Press Books, ISBN 978-0735619937
- Steve McConnell (2003). Professional Software Development: Shorter Schedules, Higher Quality Products, More Successful Projects, Enhanced Careers, Microsoft Prese s Books, ISBN 978-0321193674
- Dean Leffingwell (2007). Scaling Software Agility: Best Practices for Large Enterprises, Addison-Wesley Professional, ISBN 978-0321458193