Automatic Code Generation from Design Patterns

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Automatic Code Generation from Design Patterns

• Rohini Rajagopal

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Outline

• Code Generation
• Design Patterns
• Generative Design Patterns
• Code generation from design patterns
• Requirements for code generation

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Code Generation

• Code generation is the technique of building code
  using programs.
• These programs can range from very small helper
  scripts, to grand creations that turn abstract
  models of business logic into complete
  applications.
• The unifying feature of code generation is that
  the output of the generator is code that an
  engineer would otherwise have to write by hand.

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Code Generation when can it be used?

• Figure out how the problem can be solved by hand
  coding
• Figure out how to automate the process
• Once the requirements are known, a decision can
  be made on which generator can be used or if one
  should be developed.

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Design Patterns

• A pattern is something designed or used as a
  model for making things
• Patterns solve problems
• Patterns build on experience
• Patterns focus on human comforts
• Give designers a reference of proven design
  solutions and how to solve them
• Design patterns are different from code patterns

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Design Patterns

• Include a diagram and a description that
  contains

• Implementations
• Consequences
• Sample code
• Known uses
• Related Patterns

• Intent
• Motivation
• Applicability
• Structure
• Participants
• Collaborations

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Problems with design patterns

• They are not code
• They must be implemented each time they are
  applied
• Not enough patterns available for real world
  problems
• Code reuse is difficult
• Tools for generating design pattern code are
  still not widely available.

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Why Generative design patterns work

• General enough for a wide range of applications
• Abstraction. Ability to construct a layered
  programming model
• Tools available for automation

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Advantages of using generative design patterns

• Reduces the time needed for the engineering
  process
• Reduces programmer error
• Promotes rapid prototyping and code reuse
• Provides better overall software engineering
  benefits in terms of
• Quality
• Maintenance
• Code reuse

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Example of design pattern - Phone Order Example

• The object oriented design shows a unified,
  higher level interface to a subsystem, that makes
  it easier to use.
• Consumers encounter a Facade when ordering from
  a catalog.
• The consumer calls one number and speaks with a
  customer service representative.
• The customer service representative acts as a
  Facade, providing an interface to the order
  fulfillment department, the billing department,
  and the shipping department.

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Implementation of design patterns

• Information required to implement design patterns
• Choices for implementation trade offs and code
  generation options
• Application specific names for the following
• Participants
• Classes
• Methods
• Fields
• Variables

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Code Generation Requirements

• Convenient
• Solution has to be easily understood and be
  usable
• The solution should be comprehensive and
  complete. The user should not have to spend ages
  tweaking the output
• Non Irreversible
• Incorporation of user changes after the code has
  been generated need to be preserved or re
  applied after one of the underlying patterns has
  changed, or a new pattern has been added.

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Conclusion

• Automatic code generation adds a dimension of
  utility to design patterns
• It shows how domain concepts map into code that
  implements the pattern
• Code generated can be put to use immediately
• The process is still in its infancy

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References

• Automatic Code Generation from Design Patterns by
  Frank Budinsky, Marilyn Finnie, Patsy Yu and John
  Vlissides
• http//www.research.ibm.com/designpatterns/pubs/co
  degen.pdf
• Using Generative Design Patterns to Generate
  Parallel Code for a Distributed Memory
  Environment by Kai Tan, Duane Szafron, Jonathan
  Schaeffer, John Anvik, Steve MacDonald
• http//delivery.acm.org/10.1145/790000/781532/p203
  -tan.pdf?key1781532key20079773111collGUIDEdl
  GUIDECFID43119250CFTOKEN56673799
• Examples of Software Design Patterns
• http//www2.ing.puc.cl/jnavon/IIC2142/patexamples
  .htm
• Code generation FAQ
• http//codegeneration.net/tiki-index.php?pageFreq
  uentlyAskedQuestions
• Generating code from design patterns by Ray
  Grimmond and Christie Whitesides
• http//www.qwan.com/AboutUs/Generate.pdf