Program%20Families

1
Program Families

• CSE870 Discussion
• April 14, 2003

2
Family of Programs

• Grouping/finding COMMON functionality
• Reuse of designs/code across family members
• Pushing design decisions as late as possible

3
3 Approaches

• Classical Sequential
• Develop specific program completely
• Subsequent programs are derived from original
  program
• Identify specific points to be changed
• Complete design process BEFORE making changes for
  other family members

4
Stepwise Refinement

• Top-down approach
• Start with abstract designs
• Refine each point until you reach concrete
  functionality
• Partial design
• Intermediate points can have deviations
• Intermediate points may not be implemented
• Programming for change
• Keep intermediate nodes flexible
• Pattern Usage Strategy, Template
• Tree Shape Long and skinny

5
Stepwise Refinement

• Advantages
• No extra cost no extra specifications
• Because you reverse design decisions, you can
  still reuse all of the ancestors prior to that
  intermediate point
• Clean development cycle
• Top-down advantages narrowing the implementation
  space no synthesis problem
• Disadvantages
• Early decisions have to make many design
  decisions early in the process
• Changes to the ancestor tree can have major
  impact on more of the final designs
• Narrow family variation among family members may
  be quite small

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Module Specification

• Basic idea Decompose functionality into modules
• Module
• Collection of functions to perform specific
  service
• interface (group together collection of
  operations/data into one entity)
• Approach
• Bottom clustering of functionality into modules
• Intermediate stage is a module specification
• Can be realized by body implementations for
  specification
• Module specification is not part of final program
  code for any family member
• Tree Shape
• Broader delay design decisions until very late
  in process

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Module Specification

• Advantages
• More choices early (I.e., delay design decisions)
• Gain independence among module implementations
• Parallel development
• Information Hiding (via specifications)
• Exploits OO properties (modularity,
  encapsulation, reuse, abstraction, etc.)
• Documentation (via specifications)
• Intermediate node comprise multiple module
  specifications, thus allowing for choice among
  the modules for final functionality.

8
Module Specification

• Disadvantages
• Cost of developing specifications
• Overhead in initial specification each
  functionality must be specified (well-understood)
• More difficult abstract the services/data across
  many possible designs/implementation
• Requires master programmer experience

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When to use

• Module specification
• Use to specify services and abstract data types
  without commitments to design
• Use stepwise refinement for the parts that you
  have a clear understanding of a majority of the
  design

10
Applications of Program Families

• Operating Systems different versions
• Web browsers across vendors and within vendor
• Wysiwig vs command-line editors
• Product-line engineering
• Domain analysis/engineering

11
Frameworks

• Customize frameworks to achieve program families
• Module Specification
• Whitebox
• Delaying design decisions until late, designer
  implement as appropriate
• Stepwise Refinement
• Graybox
• Design structure is already known
• At intermediate node, you can branch to a
  different decision, but you dont need to
  backtrack to previous design decisions.