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constraints

visicalc

thinglab

logo linked turtles

smalltalk examples

turtle geo

sophie+gls

culler

education
    logo
    smalltalk
    lisp
    books
    summer school

refs.
mindstorms
world challenge
turtle geo
culler stuff

Useable Systems

The key to the wide-spread use of computing resources is the development
of  effective user interfaces. A successful example of this phenomenon
is Visicalc. This micro-based software tool

***  describe it ***

Visicalc is an exceptionally simple application of a computing technique
called "constraints". We exhibit several examples of constraint 
notions and show that there is a rich class of applications that are
potential products.  We propose to exploit that initial market immediately while
developing general tools  to assure the speedy implemenation of more
advanced applications as hardware becomes available.


Computing tools have a reputation for being formidable.

Cost

Size

Obscure communication

Mindless

No common sense

No sense of inconsistency

Irresponsible
--------------------------------------------
How to address these problems.

Cost
 micro technology

Size
 vlsi

Obscure communication
 speech/natural language communication
 graphics: visual presentation
 flexible declarative  languages

Irresponsible systems:  the difficulty!

No common sense
 deduction

No sense of inconsistency
 sense of truth

--------------------------------------------
Constraints: The kernel notions 

objects are interrelated: a change of one can affect change in another
examples: 
   visicalc
   thinglab
   gls circuit
   dpl* design rules
   turtles/physics

systems must be responsible: an inconsistency must be detectable
examples:

systems must be directable: an object must be retractable
examples:


what can be done now 
  visicalc+
  sophie+gls
  dpl
  culler+

what can be expected

 system building tools

  constraint languages
 
  expert systems


what is required now
  machines

  people

  facilities
Culler-Fried

This is one of the first  truly interactive  graphics systems.