RFC 192 (rfc192) - Page 2 of 19

Some factors which a Network Graphics Protocol must consider

RFC 192          Some Factors which a Network Graphics      12 July 1971


      1) The user of the graphics terminal should be just another
         timesharing system user.

      2) The graphics software support should interface to existing
         timesharing programs.

      3) The software support should allow technicians, engineers,
         scientist, and business analysts as well as professional
         programmers to easily create applications using a graphic
         terminal.

      4) The software support should easily allow use of new terminals
         and types of terminals as they come on the market.

      5) The software support should be expandable as experience
         indicates new facilities are required.

      6) The software support should be portable from one timesharing
         service to another.

      7) Some form of hardcopy should be available.

MULTILEVEL MODULAR APPROACH TO SYSTEM DESIGN

   If one wants to create as system which is easy to use by
   inexperienced programmers and ultimately non-programmers, one needs
   to provide powerful problem-oriented aids to program writing.  One
   has to start with the primitive machine language used to command the
   graphics system hardware and build upward.  The philosophy of design
   chosen is the one becoming more common in the computer industry,
   which is to design increasingly more powerful levels of programming
   support, each of which interfaces to its surrounding levels and
   builds on the lower levels.  It is important to try to design these
   levels more or less at the same time so that the experience with each
   will feed back on the designs of the others before they are frozen
   and difficult to change.

   One can recognize five basic levels:

      1) The basic system level:

         This level provides facilities for use of the terminal by the
         assembly language programmers.








Watson