Visual%20Programming

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Visual Programming

• Qinwei Zhu
• Jiunwei Chen

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Contents

• What is a VPL?
• Motivations
• Examples
• Advantages / Disadvantages
• Brief Survey of VPLs
• VPLs in Detail
• Prograph, VIPR
• VPL Issues and Classifications
• References

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What is a VPL?

• A programming language that uses a visual
  representation (such as graphics, drawings,
  animation or icons, partially or completely)
• A visual language manipulates visual information
  or supports visual interaction, or allows
  programming with visual expressions Golin 90
• Any system where the user writes a program using
  two or more dimensions Myers 90
• A visual language is a set of spatial
  arrangements of text-graphic symbols with a
  semantic interpretation that is used in carrying
  out communication actions in the world

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What are NOT VPLs?

• Visual Basic, Visual C, Delphi, etc.
• Still primarily textual languages with a
  graphical GUI builder
• User interface portion of the language is visual,
  the rest is not

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Motivations

• Many people think in pictures.
• Textual programming languages have proven to be
  difficult for many people to learn to use
  effectively.
• Some applications are very well suited to
  graphical development approaches.
• Scientific visualization
• System simulation

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Example 1 Factorial

• int Factorial(int n)
• if(n gt 0) return (nfactorial(n-1))
• else
• return (1)

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Forms/3 Example
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Prograph Example
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Example 2

• msc Timeout2
• instance User
• out Code to Keyboard
• endinstance
• instance Keyboard
• in Code from User out Code to Main
• endinstance
• instance Screen
• in Enter amount' from Main
• in Take card' from Main
• endinstance
• instance Main
• in Code from Keyboard
• out Enter amount' to Screen
• set Timer (10) timeout Timer out Take card'
  to Screen
• endinstance
• endmsc

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Advantages

• Fewer programming concepts
• Concreteness
• Explicit depiction of relationships
• Immediate visual feedback
• Eliminates an intermediate step in the process of
  creating a program

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Advantages (contd)

• A different conceptual framework for the
  programming process(examples)
• Parallel computation is a natural consequence of
  many visual programming paradigms

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Disadvantages

• Deutsch Limit
• The problem with visual programming is that you
  can't have more than 50 visual primitives on the
  screen at the same time.
• Some situations in which text has superiority
• documentation,
• naming to distinguish between elements that are
  of the same kind, and
• expressing well-known and compact concepts that
  are inherently textual, e.g. algebraic formulas.

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Early Systems 1966-1980

• Ambit
• AutoProgrammer
• Plan2D
• Tinker

• Grail
• Query by Example
• Pygmalion
• Outline

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Visual Systems 1981-1990

• ML-like VL
• Pict
• Formal
• SmallStar
• Hi-Visual
• PC-Titles
• ThingLab
• ARK

• Prograph
• GAL
• PIGS
• Show and Tell
• Tinker Toy
• C2
• SunPICT
• NoPumpG

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Modern Systems 1991-

• Cube
• Cantata
• Hence 1.4
• SchemePaint
• CODE 2.0
• Iconicode
• Viasvis
• MViews

• Forms/3
• AVS
• Mondrian
• ChemTrains
• HyperPascal
• Vampire
• VIPR
• SPE

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VPLs in Detail

• AVS and Khoros/Cantata (Monday)
• High-level languages
• Specific towards simulation and visualization
• Prograph, VIPR
• General-purpose VPLs
• Support for lower level features

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Prograph

• General-purpose VPL
• Object-oriented
• Data-flow driven
• Designed for Rapid Application Development (RAD)
• Developed by Pictograph Inc.
• One of the more successful general-purpose VPLs

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Data Flow Model

• Information flows through a system
• Data is transformed at certain points in the
  program
• This model can represent the system at any level
  of abstraction
• Application-level, package-level, class-level,
  operation-level, etc.

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Data Flow Model

• Little control over the order in which sections
  of a program are executed
• Operations can execute after all their input data
  has arrived

X
A
C
Y
B
Z
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Prograph Components

• Sections
• Analogous to Java packages
• Classes
• Attributes/methods
• Single inheritance support

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Prograph Components

• Methods
• Basis for control flow
• Contains the meat of the program
• Operations
• Basic executable component
• Operates on input, produces output

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HelloWorld Example
Method case
Operations
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Controls

• Attached to operations in order to control the
  flow of execution
• Contains two aspects
• The action to be taken
• Whether or not the action is a success or a
  failure
• Allows the next case to be executed, or the
  current case terminated, etc.

Next Case Control
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Factorial Example Revisited
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Prograph Users

• Generally used for in-house projects or small
  applications
• Corporate users include
• Akamai Technologies, Inc.
• Boeing
• Dow Chemical Company
• Raytheon
• Westinghouse

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VIPR

• Visual Imperative Programming
• Developed at the University of Colorado
• Almost completely visual
• Uses a nested series of rings
• Object-oriented
• Inheritance, polymorphism, etc.
• Semantics are similar to C

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Other VPLs

• LabVIEW (National Instruments)
• For development of measurement and automation
  applications
• Cube
• First 3D VPL almost completely visual
• Forms/3
• Another general-purpose VPL, emphasizing data
  abstraction
• Uses a spreadsheet metaphor

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VPL Issues

• Procedural Abstraction
• High-level vs. Low-level
• Levels of abstraction, granularity
• Data Abstraction
• Similar to the notion of data abstraction in
  conventional languages
• Control Flow
• Data-flow model
• Message passing model
• or others

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Classifications

• Purely visual languages
• Icons or other graphical representations are
  manipulated
• e.g. Cube, VIPR, Prograph,
• Hybrid text and visual systems
• Programs are created visually and then translated
  into an underlying textual language
• Usage of graphical elements in an otherwise
  textual language
• e.g. Rehearsal World

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Classifications

• Programming-by-example systems
• Teach a system how to perform a task
• e.g. Rehearsal World, Pygmalion
• Constraint-oriented systems
• Popular for simulation design
• e.g. ThingLab, ARK
• Form-based systems
• Uses a spreadsheet metaphor
• e.g. Forms/3, NoPumpG

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References

• http//www.cs.washington.edu/homes/jpower/vpl/vpl_
  home.html
• http//www.wi.leidenuniv.nl/CS/SEIS/vislang/VLcour
  se.html
• http//www-lsi.upc.es/rbaeza/cursos/vp/todo.html
• http//www.cs.berkeley.edu/maratb/cs263/
• http//www.efd.lth.se/d87man/EXJOBB/MSC.html
• http//www.ecs.soton.ac.uk/tal00r/vlangs.html