CSC/ECE 517 Fall 2007/wiki3 10 ljh

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The Agile Debate

Project Description

The Agile debate. Perhaps the most prominent controversy in o-o design today is whether it is possible to do a robust design with as little advance planning as agile methodologies recommend. Research this issue, on the Web and in the ACM DL, and report (fairly) on the major arguments of both sides, and on the evidence for both positions.


What is Plan-Driven Methodology?

Laurie Williams describes Plan-driven methods: "Plan-driven methods are those that begin with the solicitation and documentation of a set of requirements that is as complete as possible. Based on these requirements, one can then formulate a plan of development. Usually, the more complete the requirements, the better the plan." [1]

Plan-driven methodology encompasses several different processes including waterfall, Personal Software Process, and the Rational Unified Processes.

When are Plan-Driven Methods Most Appropriate?

Plan-driven methods are most appropriate when software is highly critical and the requirements can be determined to be stable at the beginning of the project.

As Barry Boehm explains, "Plan-driven methods work best when developers can determine the requirements in advance...and when the requirements remain relatively stable...This emphasis is vital for stable, safety-critical embedded software." [5]

What is Agile Methodology?

Laurie Williams describes agile methodology as:

"Agile methods are a subset of iterative and evolutionary methods (Larman, 2004; Larman and Basili, June 2003) and are based on iterative enhancement (Basili and Turner, 1975) and opportunistic development processes (Curtis, 1989). In all iterative products, each iteration is a self-contained, mini-project with activities that span requirements analysis, design, implementation, and test (Larman, 2004)."[1]

Agile methodology encompasses several different processes including Extreme Programming, Crystal, Scrum, and Feature Driven Development.


Benefits of Plan-Driven Methodology

Since Plan-Driven Methodology encompasses several different processes, the following are general benefits common to all. For more specific and elaborated benefits, look into the individual processes (waterfall, Personal Software Process, and Rational Unified Processes).

  • "Thorough documentation" [2]
  • "Detailed plans, workflow, roles, responsibilities, and work product descriptions" [2]
  • "On-going risk management" [2]
  • "Focus on verification and validation" [2]
  • "Predictability, stability, and high assurance" [3]
  • Attractive methodology for highly critical systems [4]
  • Allows for stable requirements [5]
  • Good for large teams and requirements [5]
  • Primary objective is "high assurance" [5]


Benefits of Agile Methodology

  • Allows for changing requirements [1]
  • Delivers working software frequently [1]
  • Encourages interaction between business people and developers [1]
  • Requires teams to regularly evaluate how to become more effective and modify accordingly [1]
  • "Higher customer satisfaction, lower defect rates, faster development times" [3]
  • Refactoring is inexpensive [5]
  • Good for small teams and requirements [5]
  • Primary objective is "rapid value" [5]


Can Agile Development Actually Produce a Robust Design?

Yes. http://portal.acm.org/citation.cfm?id=604255&coll=ACM&dl=ACM&CFID=8022253&CFTOKEN=18011744 http://portal.acm.org/citation.cfm?id=1062473&coll=ACM&dl=ACM&CFID=8022253&CFTOKEN=18011744 http://portal.acm.org/citation.cfm?id=1030005&coll=ACM&dl=ACM&CFID=8022253&CFTOKEN=18011744


What Methodology Is Best?

While some will argue strongly for one methodology or the other, many software engineering teams are migrating to a hybrid methodology. Barry Beohm and Richard Turner suggest five critical dimensions when determining which methodology to use: size, criticality, dynamism, personnel, and culture [3].

"Both agile and plan-driven methods have a home ground of project characteristics in which each clearly works best, and where the other will have difficulties. Hybrid approaches that combine both methods are feasible and necessary for projects that combine a mix of agile and plan-driven home ground characteristics." [5]

For a fantastic spider-like diagram of how to choose the methodology best for your team, view Dr. Laurie Williams' slides: Choosing Your Software Development Process: Agile or Plan-driven?. Slide #4 allows you to chart where your team lies in the five critical dimensions and determine whether plan-driven, agile, or a hybrid is best for you.


Suggested Links


References

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