SYNTAX.TXT

                            (The Amateur Reasoner v1.7.0)

                                 Norman Newman
                                Kibbutz  Tsor'a
                               MP Shimshon 99705
                                    Israel
                                 November 1990


This document explains the syntax needed for rule files which are used as
input for the Amateur Reasoner inference engine. The syntax is described
here using Backus-Naur form, where
         ::=  denotes 'is equivalent to'
         |    denotes 'or'
         <text> indicates that 'text' must appear literally.

program    ::= statements
statements ::= stmt | stmt statements
stmt       ::= rule | goal | prompt | comment | intro

rule       ::= <if> prem <then> prem <.>
prem       ::= premise | premise <&> prem
premise    ::= text <=> text

goal       ::= <goal (> token <)>

prompt     ::= <prompt (> text <) = > text <?>
intro      ::= <intro = > text <.>
comment    ::= <!> text <!>
text       ::= token | token text

token      ::= any combination of alphanumeric characters upto a maximum
               length of 255. A token may not include the characters
               ( ) , . = & ? !

Of the five kinds of statement, the goal statement must appear only once; a
second goal statement will be flagged as an error but ignored. The 'intro'
statement is optional, but if it appears, it may do so only once; more than
one intro statement is a fatal parsing error. All the other statement forms
are optional, although a rule file without rules is not very useful.

Comments may be inserted anywhere in the program (although not inside
tokens) and are delimited by exclamation marks (!). Comments may not be
nested. It should be noted that comments add to the clarity of a program
but cause slower parsing.

The Amateur Reasoner is case sensitive, although the four keywords (if, goal,
prompt and goal) may be entered in upper or lower case. Rule files are
free-form ASCII files and empty lines or indentation may be introduced at
will to enhance readability.

The file 'animal' is an example of a rule file which demonstrates the
syntactic forms and rules.

The program is invoked by simply typing 'amateur' at the DOS prompt. The
name of the rule file may be passed as an optional parameter; the program
will prompt for a rule file if one is not given. There is no default
extension for the rule file. If the environmental variable EXPERT$ is
defined (by adding the line 'SET EXPERT$=<directory>' to your AUTOEXEC.BAT
file), the program will be able to find your rule files without difficulty.
If this variable is not defined, and the rule file is not in the current
directory, its name must be prefaced with its complete path. Examples of
invocation -

       C> amateur animal

       C> amateur

       C> amateur c:\ai\animal

Comments, queries and bug reports are cordially invited (although I hope
that there won't be any of the third category!).