Evolution, Architecture, and Metamorphosis

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Evolution, Architecture, and Metamorphosis

• By Brian Foote and Joseph Yoder
• University of Illinois
• Presented by Gleyner Garden

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About the Authors

• Both involved in researching object oriented
  programming especially when it comes to design
  and reuse at the University of Illinois
• Collaborated on this paper to explore new
  approaches to software development for Caterpillar

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Introduction

• Design Pattern definition
• Software Tectonics
• Flexible Foundations
• Metamorphosis

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Design Patterns

• According to Object Oriented and Classical
  Software Engineering, a pattern is a solution to
  a general design problem in the form of a set of
  interacting classes that have to be customized to
  create a specific design
• Also can be seen as a partial solution to a
  common problem

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Widget Generator

• Tool that uses the set of classes created by the
  widget generator

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Abstract Factory Pattern

• Abstract classes and abstract (virtual) methods
• The interfaces between client and program and
  generator are abstract
• The application program is uncoupled from the
  specific operating system

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Patterns and Reusability

• If a design pattern is reused, then an
  implementation of that pattern probably can also
  be reused.
• Motivation for reusability
• Example GTE Data services implemented a
  successful scheme which saved the company 10
  million in 5 years

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Back to our Paper

• Foote and Yoder wanted to bring this sort of
  success to the Caterpillar corporation
• By doing so would allow Caterpillar to confront
  rapid change Software that cannot adapt as
  requirements change will perish

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Software Tectonics

• A high-level pattern which fulfills the need to
  deal with steady and unrelenting change over a
  long period of time
• Name derived by analogy of the benefits of many
  small earthquakes removing stress over a period
  of time as opposed to a sudden catastrophic one
• Gives the ability to tailor a system to meet
  individual needs by adapting to change as
  requirements change in a series of small,
  controlled steps
• By making a system tailorable, it greatly
  increases its reuse potential

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Examples of Software Tectonics

• Customizable desktops
• Short-cut creation
• Modification of existing abstract classes to meet
  needs

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Flexible Foundations

• Used to resolve some of the forces unleashed by
  the first by showing how to construct systems
  that can cope with change
• Name derived again from earthquake analogy
• Allows for selective exposure of the internal
  architecture of the system so that the elements
  of this architecture can serve as basis for
  changes and extensions (substructure, not source
  code)
• A flexible system that can easily be changed by
  its developers which will allow for fulfillments
  of new unexpected needs

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Example of Flexible Foundations

• Dupont Model
• graphical model of a view of Profit/Loss
  statements for businesses. It provides a quick
  way for managers and accountants to view their
  return on assets
• A common interface widget that is used many
  times. By adding a "DuPont widget" to the visual
  builder with methods for the automatic generation
  of related code, the developer can quickly tailor
  different DuPont models to meet the needs of
  different users

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Metamorphosis

• Helps to resolve the forces that arise in
  evolving systems by providing a means by which a
  system's behavior can be augmented without
  changing its primary interface.
• Previous design pattern allows users to add
  features, this one allows them to change features
• Further extends the life of software

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Analogy of Metamorphosis

• There are two ways to change what happens
  on-stage during a play. The most direct way is to
  change the script, but you can also change the
  actors Jim Carey VS. Anthony Hopkins
• If one wants to change the way a program works,
  one could change its code or data directly, or
  change the way that some underlying element of
  the system on which the application depends works
• Example extensions to existing tools can be
  incorporated in the menus for other tools.
  Instead of creating a whole new tool you can adds
  capabilities to the existing tool. In order to do
  this, the tool's menus must be designed using a
  metamorphosis pattern

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Evolution, Architecture, and Metamorphosis

• To be successful, software has to be able to
  rapidly adapt to changing conditions and
  requirements. To cope with this fact, software
  researchers and developers must find new ways to
  confront the need for continual evolution.
• Software must be designed so that it can change
  with the requirements that drive its evolution
• These design patterns when used with object
  oriented programs will allow for change and in
  doing so, will decrease maintenance and increase
  the lifespan of a software product

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Conclusion by SW Author Brian Cox

• Software is not at all like wood or steel. Its
  paint does not chip and it does not rust or rot.
  Software does not need dusting, waxing, or
  cleaning. It often does have faults that do need
  attention, but this is not maintenance, but
  repair. Repair is fixing something that has been
  broken by tinkering with it or something that has
  been broken all along. Conversely, as the
  environment around software changes, energy must
  be expended to keep it current. This is not
  maintenance holding steady to prevent decline.
  Evolution is changing to move ahead.

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Questions/Comments

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