AntiPatterns

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AntiPatterns

• Nagesh Arkalgud
• CSCI 577B Spring 2006

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Presentation Outline

• What are Anti-patterns?
• Why study anti patterns?
• Differences between design patterns and anti
  patterns
• Common software anti patterns
• Template for an anti pattern
• Applying anti patterns to a real problem
• Applying anti pattern solution to the 577b
  project
• Conclusion

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References

• Web References
• http//www.csc.uvic.ca/hausi/480/lectures/antipat
  terns.pdf
• http//www.serve.com/hibc/
• http//en.wikipedia.org/wiki/Antipattern
• Text References
• Brown, Malveau, McCormick III, Mowbray
  AntiPatterns Refactoring Software,
  Architectures, and Projects in Crisis John Wiley
  Sons, 1998

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The Need For Anti Patterns?

• The majority of published works in software
  sciences have focused on positive and
  constructive solutions
• AntiPatterns are derived by looking at the
  negative solutions
• Def. An AntiPattern describes a commonly
  occurring solution to a problem that generates
  decidedly negative consequences.
• The purpose of cataloguing antiPatterns is so
  they can be recognized and remedied
  (refactored).

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Why Study AntiPatterns?

• Provide a method of efficiently mapping a general
  situation to a specific class of solutions.
• Provide real world experience in recognizing
  recurring problems in the software industry
• Provide a common vocabulary for identifying
  problems and discussing solutions.
• Support the holistic resolution of conflicts

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Differences between Design Patterns and
AntiPatterns

• Design patterns often evolve into an
  AntiPattern
• Design pattern becomes an antipattern when it
  causes more problems than it solves
• Procedural programming was a great design
  pattern in the 60s and 70s
• Today it is an AntiPattern
• Object-oriented programming is today a
  practiced pattern ...

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AntiPattern Structure

• Description of the general form
• Symptoms on how to recognize the general form
• Causes that led to the general form
• Consequences of the general form
• Refactored solution on how to change the
  AntiPattern into a healthier situation

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Software AntiPatterns

• Spaghetti Code
• Stovepipe System
• Analysis Paralysis
• Design By Committee
• God Class
• Mythical Man Month
• Death March Project

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AntiPattern The Blob (aka The God Class)

• Scale Application
• Symptoms
• One big class, hundreds of unrelated methods
• Many methods with no arguments
• Cause lack of design experience
• Refactored Solution Split into smaller classes,
  identify or categorize attributes and operations

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Conclusion

• Awareness of AntiPatterns is critical for
  reengineering projects
• Always consider a range of solutions before
  narrowing down to a particular style of
  implementation
• Dont use antipatterns to exacerbate negativity
• Avoid the use of the Golden Hammer excessive use
  of one pattern. There are at least 192 software
  patterns 23 Gamma patterns, 17 Buschmann
  patterns, 72 analysis patterns, 38 CORBA
  patterns, 42 antipatterns
• Consider AntiPatterns next time you sign on to a
  new project

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Final Questions?