Visual Builders: Framework Design Issues

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Visual Builders Framework Design Issues

• By
• Vandana Gupta
• 03/02/00

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Good Framework Design

• Must cater to requirements of
• Direct Coders
• Visual Programmers

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Parts

• Definition A class with special characteristics
  to support Visual programming and code generation
• eg JavaBean
• Part Interface 3 programming Interface features
• Attributes
• Actions
• Events

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Part Interfaces

• Attribute Interface provides access to
  properties of a part
• return value
• set value
• notify on change
• Action Interface provides access to behavior of
  a part
• Event Interface to notify other parts of
  changes in a part
• change in state
• change in value of a parts attribute

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Connecting Part Features

• Parts connected to build larger composite parts
  or entire applications
• Kinds of connections
• Event-to-action execute an action when a
  certain event occurs
• AttributeChangeEvent-to-action start an action
  when an attribute changes value
• Attribute-to-attribute link two attributes(data
  valus) together so that they always stay the same
• Event-to-script cause a script to run whenever
  a certain event occurs

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Classes and Parts

• Difference between parts and classes
• Parts can notify other parts about changes to
  themselves, triggering other processing
• Converting Classes into Parts (enabling classes
  for visual programming)
• Implementing notification
• implies more connections

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Ready-to-Wear Parts Vs. Tailor-Made Classes

• Ready-to-Wear Parts
• Good for Visual programmers
• Has large number of configuring options
• Doesnt use ancillary classes to perform its
  function
• Cannot be subclassed

• Tailor-Made Classes
• Good for Direct coders
• Less configuring options
• Can be combined with other classes using
  composition
• Can be subclassed

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Design Issues due to Code Generation

• Main factors for traditional framework design
• Ease of coding
• Performance and size
• Robustness
• Visual builder
• less weight to ease of coding
• more to
• Usability
• Configuration information
• Ability to debug, document and manage generated
  code

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Giving up some freedom for convenience

• Frameworks must adhere to standards
• Actions must support a larger variety of argument
  types for a given function, by means of
  overloading

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• Added functionality
• Name changes code regenerated
• Multiargument methods flexible syntax
• Degree
• Number of classes
• Number of connections (number of methods called
  within a block of code)

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Summary

• Change classes to parts by implementing event
  notification
• Create more self-contained, ready-to-use parts
• Follow the standards required or recommended by
  visual builder
• Provide common action or attributes in part to
  reduce number of connections needed to be made
• Test and use parts with visual builder to ensure
  number of connections are minimized
• Make parts easy to use by providing default
  parameters and supporting multiple data types as
  input to actions and attributes