[antlr-interest] Newbie question on ANTLR

[John Ibbotson]

Hi,
I'm a newcomer to ANTLR and am trying to write a grammar to parse 
controlled natural language. The idea is to parse sentences then convert 
to RDF using Jena. A colleague has already written a version in Prolog so 
I'm looking to do a Java version. My starting point is to write the 
following grammar:

rule: cesentence;

cesentence:             sentence FSTOP;
sentence:               declarative;
declarative:            simpleds name?;
simpleds:               ('there is' existentialnp) |
                        (nounp verbp) |
                        ('it is' ('true' | 'false' | 'unknown') 'that' 
generalproposition);
existentialnp:          ('a' | 'an') description;
description:            noun namedecl? relativeclause?;
namedecl:               ('named' name) |
                        variable |
                        ('known as' name);
nounp:                  existentialnp |
                        referentialnp;
verbp:                  simplevp ('and' simplevp)*;
simplevp:               (('has' | 'does not have') simplenp 'as' 
functionalnoun);
verbcomp:               simplenp;
simplenp:               ('(' simplenp ')') |
                        existentialnp |
                        referentialnp;
referentialnp:          ('the' noun (name | variable)) |
                        variable |
                        ('the type' noun) |
                        ('the' noun 'known as' name);
generalproposition:     simpleds |
                        QUOTE;
relativeclause:         ('that' verbp) |
                        ('described as' QUOTE);

// CE Lexical categories
name:                   STRNG;
noun:                   'person';
functionalnoun: 'brother';
variable:               UCSTR;

// Terminators
FSTOP:          '.';
UCSTR:                  ('A'..'Z' | '0'..'9')+;                 // String 
with upper and digits
STRNG:          (UCSTR | 'a'..'z')+;                    // String with 
upper, lower and digits
SPACE:                  ' ';
QUOTE:          '"' (STRNG | SPACE)* '"'; 

which was pretty straightforward. I then tested it using the interpreter 
(Eclipse IDE plugin) on the following sentence:

there is a person named Fred.

but the parser falls over on the existentialnp rule. Any help appreciated.

Regards,
John

John Ibbotson PhD CEng FIET
Master Inventor
ITA  Project, Emerging Technology Services 
Hursley Park, MP137, Winchester, Hants. SO21 2JN, UK 

Tel:         +44 1962 815188 
Email:     john_ibbotson at uk.ibm.com 

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