Browse Prior Art Database

Command Correction for Operator Consoles

IP.com Disclosure Number: IPCOM000104181D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 123K

Publishing Venue

IBM

Related People

Brisson, JP: AUTHOR [+3]

Abstract

Disclosed is a technique used to improve the human factors characteristics of operator commands. The technique employs command correction when possible and enhanced syntax error messages otherwise. This work is based upon a pre-existing IBM internal tool called PERG (Parser and Error Recovery Generator), which generates program code for parsers based on given grammar. A technique to apply the syntax correction potential supplied by PERG to operator commands through differentiation of safe and dangerous corrections is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 45% of the total text.

Command Correction for Operator Consoles

      Disclosed is a technique used to improve the human factors
characteristics of operator commands.  The technique employs command
correction when possible and enhanced syntax error messages
otherwise.  This work is based upon a pre-existing IBM internal tool
called PERG (Parser and Error Recovery Generator), which generates
program code for parsers based on given grammar.  A technique to
apply the syntax correction potential supplied by PERG to operator
commands through differentiation of safe and dangerous corrections is
disclosed.

      Many operating systems, including MVS/ESA*, use a somewhat
unforgiving user interface for the operator console.  The result is
poor human factors which can increase the time required for an
operator to enter a critical system command.

      MVS/ESA system commands tend to be of a cryptic nature in
general.  It can be difficult to remember a command's syntax, which
often leads to the invalid specification of the command.  The
resulting syntax error messages can often be of little help and the
operator is forced to verify the command syntax in the MVS/ESA
Systems Commands Reference.  It is entirely possible that the
operator knew the command syntax very well, but simply made an error
typing the command.

      There are circumstances involving system availability when the
operator is under pressure to enter a command.  The resulting stress
can make it quite easy to improperly enter a command.  In addition,
the time required to correct the command or look up the syntax may be
precious.  The useability of the operator command interface is of
critical importance during such times.

      The technique used to solve the problem follows the basic
premise of correcting an invalid command for safe syntax errors or
providing an indication of proper syntax for dangerous syntax errors.
The characteristics of safe and dangerous syntax errors will be
described along with a technique to differentiate them using PERG.

      The intent of the recovery code generated by PERG is to
continue parsing after a syntax error is detected.  For example, if
one were to write a PASCAL compiler, it would be very desirable that
the compile would not be terminated at the point of the first error.
The goal is to keep going and find more errors.  In order to do this,
the PERG-generated code will make insertions and or deletions of
tokens around the error point in order to create a syntax which is
correct as specified by the grammar productions.  The decision of
which token to insert is directly related to the order of the grammar
productions for a particular non-terminal symbol.  PERG will always
make a correction and the corrections made will be grammatically
valid.

      When this method is used in the compiler example, the token
inserted to make the syntax correct is not of critical importance.
The user can review the error messages and fix the pro...